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* file: remove __receive_fd()Christian Brauner2023-12-121-1/+1
| | | | | | | | | | | | Honestly, there's little value in having a helper with and without that int __user *ufd argument. It's just messy and doesn't really give us anything. Just expose receive_fd() with that argument and get rid of that helper. Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-5-e73ca6f4ea83@kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Christian Brauner <brauner@kernel.org>
* pidfd: prevent a kernel-doc warningRandy Dunlap2023-09-191-1/+1
| | | | | | | | | | | | Change the comment to match the function name that the SYSCALL_DEFINE() macros generate to prevent a kernel-doc warning. kernel/pid.c:628: warning: expecting prototype for pidfd_open(). Prototype was for sys_pidfd_open() instead Link: https://lkml.kernel.org/r/20230912060822.2500-1-rdunlap@infradead.org Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Christian Brauner <brauner@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* memfd: replace ratcheting feature from vm.memfd_noexec with hierarchyAleksa Sarai2023-08-211-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This sysctl has the very unusual behaviour of not allowing any user (even CAP_SYS_ADMIN) to reduce the restriction setting, meaning that if you were to set this sysctl to a more restrictive option in the host pidns you would need to reboot your machine in order to reset it. The justification given in [1] is that this is a security feature and thus it should not be possible to disable. Aside from the fact that we have plenty of security-related sysctls that can be disabled after being enabled (fs.protected_symlinks for instance), the protection provided by the sysctl is to stop users from being able to create a binary and then execute it. A user with CAP_SYS_ADMIN can trivially do this without memfd_create(2): % cat mount-memfd.c #include <fcntl.h> #include <string.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <linux/mount.h> #define SHELLCODE "#!/bin/echo this file was executed from this totally private tmpfs:" int main(void) { int fsfd = fsopen("tmpfs", FSOPEN_CLOEXEC); assert(fsfd >= 0); assert(!fsconfig(fsfd, FSCONFIG_CMD_CREATE, NULL, NULL, 2)); int dfd = fsmount(fsfd, FSMOUNT_CLOEXEC, 0); assert(dfd >= 0); int execfd = openat(dfd, "exe", O_CREAT | O_RDWR | O_CLOEXEC, 0782); assert(execfd >= 0); assert(write(execfd, SHELLCODE, strlen(SHELLCODE)) == strlen(SHELLCODE)); assert(!close(execfd)); char *execpath = NULL; char *argv[] = { "bad-exe", NULL }, *envp[] = { NULL }; execfd = openat(dfd, "exe", O_PATH | O_CLOEXEC); assert(execfd >= 0); assert(asprintf(&execpath, "/proc/self/fd/%d", execfd) > 0); assert(!execve(execpath, argv, envp)); } % ./mount-memfd this file was executed from this totally private tmpfs: /proc/self/fd/5 % Given that it is possible for CAP_SYS_ADMIN users to create executable binaries without memfd_create(2) and without touching the host filesystem (not to mention the many other things a CAP_SYS_ADMIN process would be able to do that would be equivalent or worse), it seems strange to cause a fair amount of headache to admins when there doesn't appear to be an actual security benefit to blocking this. There appear to be concerns about confused-deputy-esque attacks[2] but a confused deputy that can write to arbitrary sysctls is a bigger security issue than executable memfds. /* New API */ The primary requirement from the original author appears to be more based on the need to be able to restrict an entire system in a hierarchical manner[3], such that child namespaces cannot re-enable executable memfds. So, implement that behaviour explicitly -- the vm.memfd_noexec scope is evaluated up the pidns tree to &init_pid_ns and you have the most restrictive value applied to you. The new lower limit you can set vm.memfd_noexec is whatever limit applies to your parent. Note that a pidns will inherit a copy of the parent pidns's effective vm.memfd_noexec setting at unshare() time. This matches the existing behaviour, and it also ensures that a pidns will never have its vm.memfd_noexec setting *lowered* behind its back (but it will be raised if the parent raises theirs). /* Backwards Compatibility */ As the previous version of the sysctl didn't allow you to lower the setting at all, there are no backwards compatibility issues with this aspect of the change. However it should be noted that now that the setting is completely hierarchical. Previously, a cloned pidns would just copy the current pidns setting, meaning that if the parent's vm.memfd_noexec was changed it wouldn't propoagate to existing pid namespaces. Now, the restriction applies recursively. This is a uAPI change, however: * The sysctl is very new, having been merged in 6.3. * Several aspects of the sysctl were broken up until this patchset and the other patchset by Jeff Xu last month. And thus it seems incredibly unlikely that any real users would run into this issue. In the worst case, if this causes userspace isues we could make it so that modifying the setting follows the hierarchical rules but the restriction checking uses the cached copy. [1]: https://lore.kernel.org/CABi2SkWnAgHK1i6iqSqPMYuNEhtHBkO8jUuCvmG3RmUB5TKHJw@mail.gmail.com/ [2]: https://lore.kernel.org/CALmYWFs_dNCzw_pW1yRAo4bGCPEtykroEQaowNULp7svwMLjOg@mail.gmail.com/ [3]: https://lore.kernel.org/CALmYWFuahdUF7cT4cm7_TGLqPanuHXJ-hVSfZt7vpTnc18DPrw@mail.gmail.com/ Link: https://lkml.kernel.org/r/20230814-memfd-vm-noexec-uapi-fixes-v2-4-7ff9e3e10ba6@cyphar.com Fixes: 105ff5339f49 ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC") Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Cc: Dominique Martinet <asmadeus@codewreck.org> Cc: Christian Brauner <brauner@kernel.org> Cc: Daniel Verkamp <dverkamp@chromium.org> Cc: Jeff Xu <jeffxu@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Shuah Khan <shuah@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* pid: use struct_size_t() helperChristian Brauner2023-07-011-1/+1
| | | | | | | | | | | | | | | | | | | | | Before commit d67790ddf021 ("overflow: Add struct_size_t() helper") only struct_size() existed, which expects a valid pointer instance containing the flexible array. However, when we determine the default struct pid allocation size for the associated kmem cache of a pid namespace we need to take the nesting depth of the pid namespace into account without an variable instance necessarily being available. In commit b69f0aeb0689 ("pid: Replace struct pid 1-element array with flex-array") we used to handle this the old fashioned way and cast NULL to a struct pid pointer type. However, we do apparently have a dedicated struct_size_t() helper for exactly this case. So switch to that. Suggested-by: Kees Cook <keescook@chromium.org> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* pid: Replace struct pid 1-element array with flex-arrayKees Cook2023-06-301-2/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For pid namespaces, struct pid uses a dynamically sized array member, "numbers". This was implemented using the ancient 1-element fake flexible array, which has been deprecated for decades. Replace it with a C99 flexible array, refactor the array size calculations to use struct_size(), and address elements via indexes. Note that the static initializer (which defines a single element) works as-is, and requires no special handling. Without this, CONFIG_UBSAN_BOUNDS (and potentially CONFIG_FORTIFY_SOURCE) will trigger bounds checks: https://lore.kernel.org/lkml/20230517-bushaltestelle-super-e223978c1ba6@brauner Cc: Christian Brauner <brauner@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Jeff Xu <jeffxu@google.com> Cc: Andreas Gruenbacher <agruenba@redhat.com> Cc: Daniel Verkamp <dverkamp@chromium.org> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Jeff Xu <jeffxu@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Luis Chamberlain <mcgrof@kernel.org> Cc: Frederic Weisbecker <frederic@kernel.org> Reported-by: syzbot+ac3b41786a2d0565b6d5@syzkaller.appspotmail.com [brauner: dropped unrelated changes and remove 0 with NULL cast] Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* pid: add pidfd_prepare()Christian Brauner2023-04-031-12/+7
| | | | | | | | | | | | Add a new helper that allows to reserve a pidfd and allocates a new pidfd file that stashes the provided struct pid. This will allow us to remove places that either open code this function or that call pidfd_create() but then have to call close_fd() because there are still failure points after pidfd_create() has been called. Reviewed-by: Jan Kara <jack@suse.cz> Message-Id: <20230327-pidfd-file-api-v1-1-5c0e9a3158e4@kernel.org> Signed-off-by: Christian Brauner <brauner@kernel.org>
* gfs2: Add glockfd debugfs fileAndreas Gruenbacher2022-06-291-0/+1
| | | | | | | | | | | | | | | | | | When a process has a gfs2 file open, the file is keeping a reference on the underlying gfs2 inode, and the inode is keeping the inode's iopen glock held in shared mode. In other words, the process depends on the iopen glock of each open gfs2 file. Expose those dependencies in a new "glockfd" debugfs file. The new debugfs file contains one line for each gfs2 file descriptor, specifying the tgid, file descriptor number, and glock name, e.g., 1601 6 5/816d This list is compiled by iterating all tasks on the system using find_ge_pid(), and all file descriptors of each task using task_lookup_next_fd_rcu(). To make that work from gfs2, export those two functions. Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
* pid: add pidfd_get_task() helperChristian Brauner2021-10-141-0/+36
| | | | | | | | | | | | | | | | | | | The number of system calls making use of pidfds is constantly increasing. Some of those new system calls duplicate the code to turn a pidfd into task_struct it refers to. Give them a simple helper for this. Link: https://lore.kernel.org/r/20211004125050.1153693-2-christian.brauner@ubuntu.com Link: https://lore.kernel.org/r/20211011133245.1703103-2-brauner@kernel.org Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Matthew Bobrowski <repnop@google.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jan Kara <jack@suse.cz> Cc: Minchan Kim <minchan@kernel.org> Reviewed-by: Matthew Bobrowski <repnop@google.com> Acked-by: David Hildenbrand <david@redhat.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
* kernel/pid.c: implement additional checks upon pidfd_create() parametersMatthew Bobrowski2021-08-101-4/+7
| | | | | | | | | | | | | | | By adding the pidfd_create() declaration to linux/pid.h, we effectively expose this function to the rest of the kernel. In order to avoid any unintended behavior, or set false expectations upon this function, ensure that constraints are forced upon each of the passed parameters. This includes the checking of whether the passed struct pid is a thread-group leader as pidfd creation is currently limited to such pid types. Link: https://lore.kernel.org/r/2e9b91c2d529d52a003b8b86c45f866153be9eb5.1628398044.git.repnop@google.com Signed-off-by: Matthew Bobrowski <repnop@google.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Jan Kara <jack@suse.cz>
* kernel/pid.c: remove static qualifier from pidfd_create()Matthew Bobrowski2021-08-101-1/+3
| | | | | | | | | | | | | With the idea of returning pidfds from the fanotify API, we need to expose a mechanism for creating pidfds. We drop the static qualifier from pidfd_create() and add its declaration to linux/pid.h so that the pidfd_create() helper can be called from other kernel subsystems i.e. fanotify. Link: https://lore.kernel.org/r/0c68653ec32f1b7143301f0231f7ed14062fd82b.1628398044.git.repnop@google.com Signed-off-by: Matthew Bobrowski <repnop@google.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Jan Kara <jack@suse.cz>
* Merge branch 'exec-update-lock-for-v5.11' of ↵Linus Torvalds2020-12-151-2/+2
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull exec-update-lock update from Eric Biederman: "The key point of this is to transform exec_update_mutex into a rw_semaphore so readers can be separated from writers. This makes it easier to understand what the holders of the lock are doing, and makes it harder to contend or deadlock on the lock. The real deadlock fix wound up in perf_event_open" * 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: exec: Transform exec_update_mutex into a rw_semaphore
| * exec: Transform exec_update_mutex into a rw_semaphoreEric W. Biederman2020-12-101-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Recently syzbot reported[0] that there is a deadlock amongst the users of exec_update_mutex. The problematic lock ordering found by lockdep was: perf_event_open (exec_update_mutex -> ovl_i_mutex) chown (ovl_i_mutex -> sb_writes) sendfile (sb_writes -> p->lock) by reading from a proc file and writing to overlayfs proc_pid_syscall (p->lock -> exec_update_mutex) While looking at possible solutions it occured to me that all of the users and possible users involved only wanted to state of the given process to remain the same. They are all readers. The only writer is exec. There is no reason for readers to block on each other. So fix this deadlock by transforming exec_update_mutex into a rw_semaphore named exec_update_lock that only exec takes for writing. Cc: Jann Horn <jannh@google.com> Cc: Vasiliy Kulikov <segoon@openwall.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Bernd Edlinger <bernd.edlinger@hotmail.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Christopher Yeoh <cyeoh@au1.ibm.com> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: Sargun Dhillon <sargun@sargun.me> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Fixes: eea9673250db ("exec: Add exec_update_mutex to replace cred_guard_mutex") [0] https://lkml.kernel.org/r/00000000000063640c05ade8e3de@google.com Reported-by: syzbot+db9cdf3dd1f64252c6ef@syzkaller.appspotmail.com Link: https://lkml.kernel.org/r/87ft4mbqen.fsf@x220.int.ebiederm.org Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
* | Merge tag 'fixes-v5.11' of ↵Linus Torvalds2020-12-141-1/+1
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux Pull misc fixes from Christian Brauner: "This contains several fixes which felt worth being combined into a single branch: - Use put_nsproxy() instead of open-coding it switch_task_namespaces() - Kirill's work to unify lifecycle management for all namespaces. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This work allows us to unify the type of the counters and reduces maintenance cost by moving the counter in one place and indicating that basic lifetime management is identical for all namespaces. - Peilin's fix adding three byte padding to Dmitry's PTRACE_GET_SYSCALL_INFO uapi struct to prevent an info leak. - Two smal patches to convert from the /* fall through */ comment annotation to the fallthrough keyword annotation which I had taken into my branch and into -next before df561f6688fe ("treewide: Use fallthrough pseudo-keyword") made it upstream which fixed this tree-wide. Since I didn't want to invalidate all testing for other commits I didn't rebase and kept them" * tag 'fixes-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: nsproxy: use put_nsproxy() in switch_task_namespaces() sys: Convert to the new fallthrough notation signal: Convert to the new fallthrough notation time: Use generic ns_common::count cgroup: Use generic ns_common::count mnt: Use generic ns_common::count user: Use generic ns_common::count pid: Use generic ns_common::count ipc: Use generic ns_common::count uts: Use generic ns_common::count net: Use generic ns_common::count ns: Add a common refcount into ns_common ptrace: Prevent kernel-infoleak in ptrace_get_syscall_info()
| * pid: Use generic ns_common::countKirill Tkhai2020-08-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Switch over pid namespaces to use the newly introduced common lifetime counter. Currently every namespace type has its own lifetime counter which is stored in the specific namespace struct. The lifetime counters are used identically for all namespaces types. Namespaces may of course have additional unrelated counters and these are not altered. This introduces a common lifetime counter into struct ns_common. The ns_common struct encompasses information that all namespaces share. That should include the lifetime counter since its common for all of them. It also allows us to unify the type of the counters across all namespaces. Most of them use refcount_t but one uses atomic_t and at least one uses kref. Especially the last one doesn't make much sense since it's just a wrapper around refcount_t since 2016 and actually complicates cleanup operations by having to use container_of() to cast the correct namespace struct out of struct ns_common. Having the lifetime counter for the namespaces in one place reduces maintenance cost. Not just because after switching all namespaces over we will have removed more code than we added but also because the logic is more easily understandable and we indicate to the user that the basic lifetime requirements for all namespaces are currently identical. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/159644979226.604812.7512601754841882036.stgit@localhost.localdomain Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
* | pid: move pidfd_get_pid() to pid.cMinchan Kim2020-10-181-0/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | process_madvise syscall needs pidfd_get_pid function to translate pidfd to pid so this patch move the function to kernel/pid.c. Suggested-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Suren Baghdasaryan <surenb@google.com> Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jann Horn <jannh@google.com> Cc: Brian Geffon <bgeffon@google.com> Cc: Daniel Colascione <dancol@google.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: John Dias <joaodias@google.com> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Oleksandr Natalenko <oleksandr@redhat.com> Cc: Sandeep Patil <sspatil@google.com> Cc: SeongJae Park <sj38.park@gmail.com> Cc: SeongJae Park <sjpark@amazon.de> Cc: Shakeel Butt <shakeelb@google.com> Cc: Sonny Rao <sonnyrao@google.com> Cc: Tim Murray <timmurray@google.com> Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Florian Weimer <fw@deneb.enyo.de> Cc: <linux-man@vger.kernel.org> Link: http://lkml.kernel.org/r/20200302193630.68771-5-minchan@kernel.org Link: http://lkml.kernel.org/r/20200622192900.22757-3-minchan@kernel.org Link: https://lkml.kernel.org/r/20200901000633.1920247-3-minchan@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | pidfd: support PIDFD_NONBLOCK in pidfd_open()Christian Brauner2020-09-041-5/+7
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Introduce PIDFD_NONBLOCK to support non-blocking pidfd file descriptors. Ever since the introduction of pidfds and more advanced async io various programming languages such as Rust have grown support for async event libraries. These libraries are created to help build epoll-based event loops around file descriptors. A common pattern is to automatically make all file descriptors they manage to O_NONBLOCK. For such libraries the EAGAIN error code is treated specially. When a function is called that returns EAGAIN the function isn't called again until the event loop indicates the the file descriptor is ready. Supporting EAGAIN when waiting on pidfds makes such libraries just work with little effort. In the following patch we will extend waitid() internally to support non-blocking pidfds. This introduces a new flag PIDFD_NONBLOCK that is equivalent to O_NONBLOCK. This follows the same patterns we have for other (anon inode) file descriptors such as EFD_NONBLOCK, IN_NONBLOCK, SFD_NONBLOCK, TFD_NONBLOCK and the same for close-on-exec flags. Suggested-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Sargun Dhillon <sargun@sargun.me> Cc: Oleg Nesterov <oleg@redhat.com> Link: https://lore.kernel.org/lkml/20200811181236.GA18763@localhost/ Link: https://github.com/joshtriplett/async-pidfd Link: https://lore.kernel.org/r/20200902102130.147672-2-christian.brauner@ubuntu.com
* Merge tag 'cap-checkpoint-restore-v5.9' of ↵Linus Torvalds2020-08-041-1/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux Pull checkpoint-restore updates from Christian Brauner: "This enables unprivileged checkpoint/restore of processes. Given that this work has been going on for quite some time the first sentence in this summary is hopefully more exciting than the actual final code changes required. Unprivileged checkpoint/restore has seen a frequent increase in interest over the last two years and has thus been one of the main topics for the combined containers & checkpoint/restore microconference since at least 2018 (cf. [1]). Here are just the three most frequent use-cases that were brought forward: - The JVM developers are integrating checkpoint/restore into a Java VM to significantly decrease the startup time. - In high-performance computing environment a resource manager will typically be distributing jobs where users are always running as non-root. Long-running and "large" processes with significant startup times are supposed to be checkpointed and restored with CRIU. - Container migration as a non-root user. In all of these scenarios it is either desirable or required to run without CAP_SYS_ADMIN. The userspace implementation of checkpoint/restore CRIU already has the pull request for supporting unprivileged checkpoint/restore up (cf. [2]). To enable unprivileged checkpoint/restore a new dedicated capability CAP_CHECKPOINT_RESTORE is introduced. This solution has last been discussed in 2019 in a talk by Google at Linux Plumbers (cf. [1] "Update on Task Migration at Google Using CRIU") with Adrian and Nicolas providing the implementation now over the last months. In essence, this allows the CRIU binary to be installed with the CAP_CHECKPOINT_RESTORE vfs capability set thereby enabling unprivileged users to restore processes. To make this possible the following permissions are altered: - Selecting a specific PID via clone3() set_tid relaxed from userns CAP_SYS_ADMIN to CAP_CHECKPOINT_RESTORE. - Selecting a specific PID via /proc/sys/kernel/ns_last_pid relaxed from userns CAP_SYS_ADMIN to CAP_CHECKPOINT_RESTORE. - Accessing /proc/pid/map_files relaxed from init userns CAP_SYS_ADMIN to init userns CAP_CHECKPOINT_RESTORE. - Changing /proc/self/exe from userns CAP_SYS_ADMIN to userns CAP_CHECKPOINT_RESTORE. Of these four changes the /proc/self/exe change deserves a few words because the reasoning behind even restricting /proc/self/exe changes in the first place is just full of historical quirks and tracking this down was a questionable version of fun that I'd like to spare others. In short, it is trivial to change /proc/self/exe as an unprivileged user, i.e. without userns CAP_SYS_ADMIN right now. Either via ptrace() or by simply intercepting the elf loader in userspace during exec. Nicolas was nice enough to even provide a POC for the latter (cf. [3]) to illustrate this fact. The original patchset which introduced PR_SET_MM_MAP had no permissions around changing the exe link. They too argued that it is trivial to spoof the exe link already which is true. The argument brought up against this was that the Tomoyo LSM uses the exe link in tomoyo_manager() to detect whether the calling process is a policy manager. This caused changing the exe links to be guarded by userns CAP_SYS_ADMIN. All in all this rather seems like a "better guard it with something rather than nothing" argument which imho doesn't qualify as a great security policy. Again, because spoofing the exe link is possible for the calling process so even if this were security relevant it was broken back then and would be broken today. So technically, dropping all permissions around changing the exe link would probably be possible and would send a clearer message to any userspace that relies on /proc/self/exe for security reasons that they should stop doing this but for now we're only relaxing the exe link permissions from userns CAP_SYS_ADMIN to userns CAP_CHECKPOINT_RESTORE. There's a final uapi change in here. Changing the exe link used to accidently return EINVAL when the caller lacked the necessary permissions instead of the more correct EPERM. This pr contains a commit fixing this. I assume that userspace won't notice or care and if they do I will revert this commit. But since we are changing the permissions anyway it seems like a good opportunity to try this fix. With these changes merged unprivileged checkpoint/restore will be possible and has already been tested by various users" [1] LPC 2018 1. "Task Migration at Google Using CRIU" https://www.youtube.com/watch?v=yI_1cuhoDgA&t=12095 2. "Securely Migrating Untrusted Workloads with CRIU" https://www.youtube.com/watch?v=yI_1cuhoDgA&t=14400 LPC 2019 1. "CRIU and the PID dance" https://www.youtube.com/watch?v=LN2CUgp8deo&list=PLVsQ_xZBEyN30ZA3Pc9MZMFzdjwyz26dO&index=9&t=2m48s 2. "Update on Task Migration at Google Using CRIU" https://www.youtube.com/watch?v=LN2CUgp8deo&list=PLVsQ_xZBEyN30ZA3Pc9MZMFzdjwyz26dO&index=9&t=1h2m8s [2] https://github.com/checkpoint-restore/criu/pull/1155 [3] https://github.com/nviennot/run_as_exe * tag 'cap-checkpoint-restore-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: selftests: add clone3() CAP_CHECKPOINT_RESTORE test prctl: exe link permission error changed from -EINVAL to -EPERM prctl: Allow local CAP_CHECKPOINT_RESTORE to change /proc/self/exe proc: allow access in init userns for map_files with CAP_CHECKPOINT_RESTORE pid_namespace: use checkpoint_restore_ns_capable() for ns_last_pid pid: use checkpoint_restore_ns_capable() for set_tid capabilities: Introduce CAP_CHECKPOINT_RESTORE
| * pid: use checkpoint_restore_ns_capable() for set_tidAdrian Reber2020-07-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | Use the newly introduced capability CAP_CHECKPOINT_RESTORE to allow using clone3() with set_tid set. Signed-off-by: Adrian Reber <areber@redhat.com> Signed-off-by: Nicolas Viennot <Nicolas.Viennot@twosigma.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/20200719100418.2112740-3-areber@redhat.com Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
* | pidfd: Replace open-coded receive_fd()Kees Cook2020-07-131-13/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Replace the open-coded version of receive_fd() with a call to the new helper. Thanks to Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com> for catching a missed fput() in an earlier version of this patch. Cc: Christoph Hellwig <hch@lst.de> Cc: Jakub Kicinski <kuba@kernel.org> Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Sargun Dhillon <sargun@sargun.me> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Kees Cook <keescook@chromium.org>
* | pidfd: Add missing sock updates for pidfd_getfd()Kees Cook2020-07-131-2/+5
|/ | | | | | | | | | | | | | | | The sock counting (sock_update_netprioidx() and sock_update_classid()) was missing from pidfd's implementation of received fd installation. Add a call to the new __receive_sock() helper. Cc: Christian Brauner <christian.brauner@ubuntu.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Sargun Dhillon <sargun@sargun.me> Cc: Jakub Kicinski <kuba@kernel.org> Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org Fixes: 8649c322f75c ("pid: Implement pidfd_getfd syscall") Signed-off-by: Kees Cook <keescook@chromium.org>
* remove the no longer needed pid_alive() check in __task_pid_nr_ns()Oleg Nesterov2020-04-301-2/+1
| | | | | | | | | | | | | | Starting from 2c4704756cab ("pids: Move the pgrp and session pid pointers from task_struct to signal_struct") __task_pid_nr_ns() doesn't dereference task->group_leader, we can remove the pid_alive() check. pid_nr_ns() has to check pid != NULL anyway, pid_alive() just adds the unnecessary confusion. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
* proc: Ensure we see the exit of each process tid exactly onceEric W. Biederman2020-04-281-0/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When the thread group leader changes during exec and the old leaders thread is reaped proc_flush_pid will flush the dentries for the entire process because the leader still has it's original pid. Fix this by exchanging the pids in an rcu safe manner, and wrapping the code to do that up in a helper exchange_tids. When I removed switch_exec_pids and introduced this behavior in d73d65293e3e ("[PATCH] pidhash: kill switch_exec_pids") there really was nothing that cared as flushing happened with the cached dentry and de_thread flushed both of them on exec. This lack of fully exchanging pids became a problem a few months later when I introduced 48e6484d4902 ("[PATCH] proc: Rewrite the proc dentry flush on exit optimization"). Which overlooked the de_thread case was no longer swapping pids, and I was looking up proc dentries by task->pid. The current behavior isn't properly a bug as everything in proc will continue to work correctly just a little bit less efficiently. Fix this just so there are no little surprise corner cases waiting to bite people. -- Oleg points out this could be an issue in next_tgid in proc where has_group_leader_pid is called, and reording some of the assignments should fix that. -- Oleg points out this will break the 10 year old hack in __exit_signal.c > /* > * This can only happen if the caller is de_thread(). > * FIXME: this is the temporary hack, we should teach > * posix-cpu-timers to handle this case correctly. > */ > if (unlikely(has_group_leader_pid(tsk))) > posix_cpu_timers_exit_group(tsk); The code in next_tgid has been changed to use PIDTYPE_TGID, and the posix cpu timers code has been fixed so it does not need the 10 year old hack, so this should be safe to merge now. Link: https://lore.kernel.org/lkml/87h7x3ajll.fsf_-_@x220.int.ebiederm.org/ Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Oleg Nesterov <oleg@redhat.com> Fixes: 48e6484d4902 ("[PATCH] proc: Rewrite the proc dentry flush on exit optimization"). Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
* Merge branch 'for-linus' of ↵Linus Torvalds2020-04-101-0/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull proc fix from Eric Biederman: "A brown paper bag slipped through my proc changes, and syzcaller caught it when the code ended up in your tree. I have opted to fix it the simplest cleanest way I know how, so there is no reasonable chance for the bug to repeat" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: proc: Use a dedicated lock in struct pid
| * proc: Use a dedicated lock in struct pidEric W. Biederman2020-04-091-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | syzbot wrote: > ======================================================== > WARNING: possible irq lock inversion dependency detected > 5.6.0-syzkaller #0 Not tainted > -------------------------------------------------------- > swapper/1/0 just changed the state of lock: > ffffffff898090d8 (tasklist_lock){.+.?}-{2:2}, at: send_sigurg+0x9f/0x320 fs/fcntl.c:840 > but this lock took another, SOFTIRQ-unsafe lock in the past: > (&pid->wait_pidfd){+.+.}-{2:2} > > > and interrupts could create inverse lock ordering between them. > > > other info that might help us debug this: > Possible interrupt unsafe locking scenario: > > CPU0 CPU1 > ---- ---- > lock(&pid->wait_pidfd); > local_irq_disable(); > lock(tasklist_lock); > lock(&pid->wait_pidfd); > <Interrupt> > lock(tasklist_lock); > > *** DEADLOCK *** > > 4 locks held by swapper/1/0: The problem is that because wait_pidfd.lock is taken under the tasklist lock. It must always be taken with irqs disabled as tasklist_lock can be taken from interrupt context and if wait_pidfd.lock was already taken this would create a lock order inversion. Oleg suggested just disabling irqs where I have added extra calls to wait_pidfd.lock. That should be safe and I think the code will eventually do that. It was rightly pointed out by Christian that sharing the wait_pidfd.lock was a premature optimization. It is also true that my pre-merge window testing was insufficient. So remove the premature optimization and give struct pid a dedicated lock of it's own for struct pid things. I have verified that lockdep sees all 3 paths where we take the new pid->lock and lockdep does not complain. It is my current day dream that one day pid->lock can be used to guard the task lists as well and then the tasklist_lock won't need to be held to deliver signals. That will require taking pid->lock with irqs disabled. Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/lkml/00000000000011d66805a25cd73f@google.com/ Cc: Oleg Nesterov <oleg@redhat.com> Cc: Christian Brauner <christian.brauner@ubuntu.com> Reported-by: syzbot+343f75cdeea091340956@syzkaller.appspotmail.com Reported-by: syzbot+832aabf700bc3ec920b9@syzkaller.appspotmail.com Reported-by: syzbot+f675f964019f884dbd0f@syzkaller.appspotmail.com Reported-by: syzbot+a9fb1457d720a55d6dc5@syzkaller.appspotmail.com Fixes: 7bc3e6e55acf ("proc: Use a list of inodes to flush from proc") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
* | Merge branch 'for-linus' of ↵Linus Torvalds2020-04-021-10/+3
|\| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull exec/proc updates from Eric Biederman: "This contains two significant pieces of work: the work to sort out proc_flush_task, and the work to solve a deadlock between strace and exec. Fixing proc_flush_task so that it no longer requires a persistent mount makes improvements to proc possible. The removal of the persistent mount solves an old regression that that caused the hidepid mount option to only work on remount not on mount. The regression was found and reported by the Android folks. This further allows Alexey Gladkov's work making proc mount options specific to an individual mount of proc to move forward. The work on exec starts solving a long standing issue with exec that it takes mutexes of blocking userspace applications, which makes exec extremely deadlock prone. For the moment this adds a second mutex with a narrower scope that handles all of the easy cases. Which makes the tricky cases easy to spot. With a little luck the code to solve those deadlocks will be ready by next merge window" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (25 commits) signal: Extend exec_id to 64bits pidfd: Use new infrastructure to fix deadlocks in execve perf: Use new infrastructure to fix deadlocks in execve proc: io_accounting: Use new infrastructure to fix deadlocks in execve proc: Use new infrastructure to fix deadlocks in execve kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve kernel: doc: remove outdated comment cred.c mm: docs: Fix a comment in process_vm_rw_core selftests/ptrace: add test cases for dead-locks exec: Fix a deadlock in strace exec: Add exec_update_mutex to replace cred_guard_mutex exec: Move exec_mmap right after de_thread in flush_old_exec exec: Move cleanup of posix timers on exec out of de_thread exec: Factor unshare_sighand out of de_thread and call it separately exec: Only compute current once in flush_old_exec pid: Improve the comment about waiting in zap_pid_ns_processes proc: Remove the now unnecessary internal mount of proc uml: Create a private mount of proc for mconsole uml: Don't consult current to find the proc_mnt in mconsole_proc proc: Use a list of inodes to flush from proc ...
| * pidfd: Use new infrastructure to fix deadlocks in execveBernd Edlinger2020-03-251-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | This changes __pidfd_fget to use the new exec_update_mutex instead of cred_guard_mutex. This should be safe, as the credentials do not change before exec_update_mutex is locked. Therefore whatever file access is possible with holding the cred_guard_mutex here is also possbile with the exec_update_mutex. Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
| * proc: Remove the now unnecessary internal mount of procEric W. Biederman2020-02-281-8/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There remains no more code in the kernel using pids_ns->proc_mnt, therefore remove it from the kernel. The big benefit of this change is that one of the most error prone and tricky parts of the pid namespace implementation, maintaining kernel mounts of proc is removed. In addition removing the unnecessary complexity of the kernel mount fixes a regression that caused the proc mount options to be ignored. Now that the initial mount of proc comes from userspace, those mount options are again honored. This fixes Android's usage of the proc hidepid option. Reported-by: Alistair Strachan <astrachan@google.com> Fixes: e94591d0d90c ("proc: Convert proc_mount to use mount_ns.") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
| * proc: Use a list of inodes to flush from procEric W. Biederman2020-02-241-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Rework the flushing of proc to use a list of directory inodes that need to be flushed. The list is kept on struct pid not on struct task_struct, as there is a fixed connection between proc inodes and pids but at least for the case of de_thread the pid of a task_struct changes. This removes the dependency on proc_mnt which allows for different mounts of proc having different mount options even in the same pid namespace and this allows for the removal of proc_mnt which will trivially the first mount of proc to honor it's mount options. This flushing remains an optimization. The functions pid_delete_dentry and pid_revalidate ensure that ordinary dcache management will not attempt to use dentries past the point their respective task has died. When unused the shrinker will eventually be able to remove these dentries. There is a case in de_thread where proc_flush_pid can be called early for a given pid. Which winds up being safe (if suboptimal) as this is just an optiimization. Only pid directories are put on the list as the other per pid files are children of those directories and d_invalidate on the directory will get them as well. So that the pid can be used during flushing it's reference count is taken in release_task and dropped in proc_flush_pid. Further the call of proc_flush_pid is moved after the tasklist_lock is released in release_task so that it is certain that the pid has already been unhashed when flushing it taking place. This removes a small race where a dentry could recreated. As struct pid is supposed to be small and I need a per pid lock I reuse the only lock that currently exists in struct pid the the wait_pidfd.lock. The net result is that this adds all of this functionality with just a little extra list management overhead and a single extra pointer in struct pid. v2: Initialize pid->inodes. I somehow failed to get that initialization into the initial version of the patch. A boot failure was reported by "kernel test robot <lkp@intel.com>", and failure to initialize that pid->inodes matches all of the reported symptoms. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
* | pid: make ENOMEM return value more obviousChristian Brauner2020-03-091-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The alloc_pid() codepath used to be simpler. With the introducation of the ability to choose specific pids in 49cb2fc42ce4 ("fork: extend clone3() to support setting a PID") it got more complex. It hasn't been super obvious that ENOMEM is returned when the pid namespace init process/child subreaper of the pid namespace has died. As can be seen from multiple attempts to improve this see e.g. [1] and most recently [2]. We regressed returning ENOMEM in [3] and [2] restored it. Let's add a comment on top explaining that this is historic and documented behavior and cannot easily be changed. [1]: 35f71bc0a09a ("fork: report pid reservation failure properly") [2]: b26ebfe12f34 ("pid: Fix error return value in some cases") [3]: 49cb2fc42ce4 ("fork: extend clone3() to support setting a PID") Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
* | pid: Fix error return value in some casesCorey Minyard2020-03-081-0/+2
|/ | | | | | | | | | | | | | | | | | | | | | | | Recent changes to alloc_pid() allow the pid number to be specified on the command line. If set_tid_size is set, then the code scanning the levels will hard-set retval to -EPERM, overriding it's previous -ENOMEM value. After the code scanning the levels, there are error returns that do not set retval, assuming it is still set to -ENOMEM. So set retval back to -ENOMEM after scanning the levels. Fixes: 49cb2fc42ce4 ("fork: extend clone3() to support setting a PID") Signed-off-by: Corey Minyard <cminyard@mvista.com> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Cc: Andrei Vagin <avagin@gmail.com> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Adrian Reber <areber@redhat.com> Cc: <stable@vger.kernel.org> # 5.5 Link: https://lore.kernel.org/r/20200306172314.12232-1-minyard@acm.org [christian.brauner@ubuntu.com: fixup commit message] Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
* pid: Implement pidfd_getfd syscallSargun Dhillon2020-01-131-0/+90
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | This syscall allows for the retrieval of file descriptors from other processes, based on their pidfd. This is possible using ptrace, and injection of parasitic code to inject code which leverages SCM_RIGHTS to move file descriptors between a tracee and a tracer. Unfortunately, ptrace comes with a high cost of requiring the process to be stopped, and breaks debuggers. This does not require stopping the process under manipulation. One reason to use this is to allow sandboxers to take actions on file descriptors on the behalf of another process. For example, this can be combined with seccomp-bpf's user notification to do on-demand fd extraction and take privileged actions. One such privileged action is binding a socket to a privileged port. /* prototype */ /* flags is currently reserved and should be set to 0 */ int sys_pidfd_getfd(int pidfd, int fd, unsigned int flags); /* testing */ Ran self-test suite on x86_64 Signed-off-by: Sargun Dhillon <sargun@sargun.me> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/20200107175927.4558-3-sargun@sargun.me Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
* fork: extend clone3() to support setting a PIDAdrian Reber2019-11-151-15/+57
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The main motivation to add set_tid to clone3() is CRIU. To restore a process with the same PID/TID CRIU currently uses /proc/sys/kernel/ns_last_pid. It writes the desired (PID - 1) to ns_last_pid and then (quickly) does a clone(). This works most of the time, but it is racy. It is also slow as it requires multiple syscalls. Extending clone3() to support *set_tid makes it possible restore a process using CRIU without accessing /proc/sys/kernel/ns_last_pid and race free (as long as the desired PID/TID is available). This clone3() extension places the same restrictions (CAP_SYS_ADMIN) on clone3() with *set_tid as they are currently in place for ns_last_pid. The original version of this change was using a single value for set_tid. At the 2019 LPC, after presenting set_tid, it was, however, decided to change set_tid to an array to enable setting the PID of a process in multiple PID namespaces at the same time. If a process is created in a PID namespace it is possible to influence the PID inside and outside of the PID namespace. Details also in the corresponding selftest. To create a process with the following PIDs: PID NS level Requested PID 0 (host) 31496 1 42 2 1 For that example the two newly introduced parameters to struct clone_args (set_tid and set_tid_size) would need to be: set_tid[0] = 1; set_tid[1] = 42; set_tid[2] = 31496; set_tid_size = 3; If only the PIDs of the two innermost nested PID namespaces should be defined it would look like this: set_tid[0] = 1; set_tid[1] = 42; set_tid_size = 2; The PID of the newly created process would then be the next available free PID in the PID namespace level 0 (host) and 42 in the PID namespace at level 1 and the PID of the process in the innermost PID namespace would be 1. The set_tid array is used to specify the PID of a process starting from the innermost nested PID namespaces up to set_tid_size PID namespaces. set_tid_size cannot be larger then the current PID namespace level. Signed-off-by: Adrian Reber <areber@redhat.com> Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com> Acked-by: Andrei Vagin <avagin@gmail.com> Link: https://lore.kernel.org/r/20191115123621.142252-1-areber@redhat.com Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
* pid: use pid_has_task() in pidfd_open()Christian Brauner2019-10-171-7/+5
| | | | | | | | | | Use the new pid_has_task() helper in pidfd_open(). This simplifies the code and avoids taking rcu_read_{lock,unlock}() and leads to overall nicer code. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Link: https://lore.kernel.org/r/20191017101832.5985-5-christian.brauner@ubuntu.com
* pid: use pid_has_task() in __change_pid()Christian Brauner2019-10-171-1/+1
| | | | | | | | | | Replace hlist_empty() with the new pid_has_task() helper which is more idiomatic, easier to grep for, and unifies how callers perform this check. Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Link: https://lore.kernel.org/r/20191017101832.5985-3-christian.brauner@ubuntu.com
* kernel/pid.c: convert struct pid count to refcount_tJoel Fernandes (Google)2019-07-161-5/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | struct pid's count is an atomic_t field used as a refcount. Use refcount_t for it which is basically atomic_t but does additional checking to prevent use-after-free bugs. For memory ordering, the only change is with the following: - if ((atomic_read(&pid->count) == 1) || - atomic_dec_and_test(&pid->count)) { + if (refcount_dec_and_test(&pid->count)) { kmem_cache_free(ns->pid_cachep, pid); Here the change is from: Fully ordered --> RELEASE + ACQUIRE (as per refcount-vs-atomic.rst) This ACQUIRE should take care of making sure the free happens after the refcount_dec_and_test(). The above hunk also removes atomic_read() since it is not needed for the code to work and it is unclear how beneficial it is. The removal lets refcount_dec_and_test() check for cases where get_pid() happened before the object was freed. Link: http://lkml.kernel.org/r/20190701183826.191936-1-joel@joelfernandes.org Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com> Reviewed-by: Kees Cook <keescook@chromium.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Elena Reshetova <elena.reshetova@intel.com> Cc: Jann Horn <jannh@google.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: KJ Tsanaktsidis <ktsanaktsidis@zendesk.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge tag 'pidfd-updates-v5.3' of ↵Linus Torvalds2019-07-101-0/+71
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux Pull pidfd updates from Christian Brauner: "This adds two main features. - First, it adds polling support for pidfds. This allows process managers to know when a (non-parent) process dies in a race-free way. The notification mechanism used follows the same logic that is currently used when the parent of a task is notified of a child's death. With this patchset it is possible to put pidfds in an {e}poll loop and get reliable notifications for process (i.e. thread-group) exit. - The second feature compliments the first one by making it possible to retrieve pollable pidfds for processes that were not created using CLONE_PIDFD. A lot of processes get created with traditional PID-based calls such as fork() or clone() (without CLONE_PIDFD). For these processes a caller can currently not create a pollable pidfd. This is a problem for Android's low memory killer (LMK) and service managers such as systemd. Both patchsets are accompanied by selftests. It's perhaps worth noting that the work done so far and the work done in this branch for pidfd_open() and polling support do already see some adoption: - Android is in the process of backporting this work to all their LTS kernels [1] - Service managers make use of pidfd_send_signal but will need to wait until we enable waiting on pidfds for full adoption. - And projects I maintain make use of both pidfd_send_signal and CLONE_PIDFD [2] and will use polling support and pidfd_open() too" [1] https://android-review.googlesource.com/q/topic:%22pidfd+polling+support+4.9+backport%22 https://android-review.googlesource.com/q/topic:%22pidfd+polling+support+4.14+backport%22 https://android-review.googlesource.com/q/topic:%22pidfd+polling+support+4.19+backport%22 [2] https://github.com/lxc/lxc/blob/aab6e3eb73c343231cdde775db938994fc6f2803/src/lxc/start.c#L1753 * tag 'pidfd-updates-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: tests: add pidfd_open() tests arch: wire-up pidfd_open() pid: add pidfd_open() pidfd: add polling selftests pidfd: add polling support
| * pid: add pidfd_open()Christian Brauner2019-06-281-0/+69
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This adds the pidfd_open() syscall. It allows a caller to retrieve pollable pidfds for a process which did not get created via CLONE_PIDFD, i.e. for a process that is created via traditional fork()/clone() calls that is only referenced by a PID: int pidfd = pidfd_open(1234, 0); ret = pidfd_send_signal(pidfd, SIGSTOP, NULL, 0); With the introduction of pidfds through CLONE_PIDFD it is possible to created pidfds at process creation time. However, a lot of processes get created with traditional PID-based calls such as fork() or clone() (without CLONE_PIDFD). For these processes a caller can currently not create a pollable pidfd. This is a problem for Android's low memory killer (LMK) and service managers such as systemd. Both are examples of tools that want to make use of pidfds to get reliable notification of process exit for non-parents (pidfd polling) and race-free signal sending (pidfd_send_signal()). They intend to switch to this API for process supervision/management as soon as possible. Having no way to get pollable pidfds from PID-only processes is one of the biggest blockers for them in adopting this api. With pidfd_open() making it possible to retrieve pidfds for PID-based processes we enable them to adopt this api. In line with Arnd's recent changes to consolidate syscall numbers across architectures, I have added the pidfd_open() syscall to all architectures at the same time. Signed-off-by: Christian Brauner <christian@brauner.io> Reviewed-by: David Howells <dhowells@redhat.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Kees Cook <keescook@chromium.org> Cc: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jann Horn <jannh@google.com> Cc: Andy Lutomirsky <luto@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-api@vger.kernel.org
| * pidfd: add polling supportJoel Fernandes (Google)2019-06-281-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch adds polling support to pidfd. Android low memory killer (LMK) needs to know when a process dies once it is sent the kill signal. It does so by checking for the existence of /proc/pid which is both racy and slow. For example, if a PID is reused between when LMK sends a kill signal and checks for existence of the PID, since the wrong PID is now possibly checked for existence. Using the polling support, LMK will be able to get notified when a process exists in race-free and fast way, and allows the LMK to do other things (such as by polling on other fds) while awaiting the process being killed to die. For notification to polling processes, we follow the same existing mechanism in the kernel used when the parent of the task group is to be notified of a child's death (do_notify_parent). This is precisely when the tasks waiting on a poll of pidfd are also awakened in this patch. We have decided to include the waitqueue in struct pid for the following reasons: 1. The wait queue has to survive for the lifetime of the poll. Including it in task_struct would not be option in this case because the task can be reaped and destroyed before the poll returns. 2. By including the struct pid for the waitqueue means that during de_thread(), the new thread group leader automatically gets the new waitqueue/pid even though its task_struct is different. Appropriate test cases are added in the second patch to provide coverage of all the cases the patch is handling. Cc: Andy Lutomirski <luto@amacapital.net> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Daniel Colascione <dancol@google.com> Cc: Jann Horn <jannh@google.com> Cc: Tim Murray <timmurray@google.com> Cc: Jonathan Kowalski <bl0pbl33p@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: David Howells <dhowells@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: kernel-team@android.com Reviewed-by: Oleg Nesterov <oleg@redhat.com> Co-developed-by: Daniel Colascione <dancol@google.com> Signed-off-by: Daniel Colascione <dancol@google.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Christian Brauner <christian@brauner.io>
* | treewide: Add SPDX license identifier for missed filesThomas Gleixner2019-05-211-0/+1
|/ | | | | | | | | | | | | | | | | Add SPDX license identifiers to all files which: - Have no license information of any form - Have EXPORT_.*_SYMBOL_GPL inside which was used in the initial scan/conversion to ignore the file These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* kernel/pid.c: remove unneeded hash header fileTimmy Li2019-05-141-1/+0
| | | | | | | | | | | | | | | | Hash functions are not needed since idr is used now. Let's remove hash header file for cleanup. Link: http://lkml.kernel.org/r/20190430053319.95913-1-scuttimmy@gmail.com Signed-off-by: Timmy Li <scuttimmy@gmail.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: KJ Tsanaktsidis <ktsanaktsidis@zendesk.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Fix failure path in alloc_pid()Matthew Wilcox2018-12-281-2/+4
| | | | | | | | | | | | | The failure path removes the allocated PIDs from the wrong namespace. This could lead to us inadvertently reusing PIDs in the leaf namespace and leaking PIDs in parent namespaces. Fixes: 95846ecf9dac ("pid: replace pid bitmap implementation with IDR API") Cc: <stable@vger.kernel.org> Signed-off-by: Matthew Wilcox <willy@infradead.org> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* mm: remove include/linux/bootmem.hMike Rapoport2018-10-311-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Move remaining definitions and declarations from include/linux/bootmem.h into include/linux/memblock.h and remove the redundant header. The includes were replaced with the semantic patch below and then semi-automated removal of duplicated '#include <linux/memblock.h> @@ @@ - #include <linux/bootmem.h> + #include <linux/memblock.h> [sfr@canb.auug.org.au: dma-direct: fix up for the removal of linux/bootmem.h] Link: http://lkml.kernel.org/r/20181002185342.133d1680@canb.auug.org.au [sfr@canb.auug.org.au: powerpc: fix up for removal of linux/bootmem.h] Link: http://lkml.kernel.org/r/20181005161406.73ef8727@canb.auug.org.au [sfr@canb.auug.org.au: x86/kaslr, ACPI/NUMA: fix for linux/bootmem.h removal] Link: http://lkml.kernel.org/r/20181008190341.5e396491@canb.auug.org.au Link: http://lkml.kernel.org/r/1536927045-23536-30-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Chris Zankel <chris@zankel.net> Cc: "David S. Miller" <davem@davemloft.net> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Greentime Hu <green.hu@gmail.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Guan Xuetao <gxt@pku.edu.cn> Cc: Ingo Molnar <mingo@redhat.com> Cc: "James E.J. Bottomley" <jejb@parisc-linux.org> Cc: Jonas Bonn <jonas@southpole.se> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Ley Foon Tan <lftan@altera.com> Cc: Mark Salter <msalter@redhat.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Matt Turner <mattst88@gmail.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Simek <monstr@monstr.eu> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Paul Burton <paul.burton@mips.com> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Richard Weinberger <richard@nod.at> Cc: Rich Felker <dalias@libc.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Serge Semin <fancer.lancer@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* fork: report pid exhaustion correctlyKJ Tsanaktsidis2018-09-201-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make the clone and fork syscalls return EAGAIN when the limit on the number of pids /proc/sys/kernel/pid_max is exceeded. Currently, when the pid_max limit is exceeded, the kernel will return ENOSPC from the fork and clone syscalls. This is contrary to the documented behaviour, which explicitly calls out the pid_max case as one where EAGAIN should be returned. It also leads to really confusing error messages in userspace programs which will complain about a lack of disk space when they fail to create processes/threads for this reason. This error is being returned because alloc_pid() uses the idr api to find a new pid; when there are none available, idr_alloc_cyclic() returns -ENOSPC, and this is being propagated back to userspace. This behaviour has been broken before, and was explicitly fixed in commit 35f71bc0a09a ("fork: report pid reservation failure properly"), so I think -EAGAIN is definitely the right thing to return in this case. The current behaviour change dates from commit 95846ecf9dac ("pid: replace pid bitmap implementation with IDR AIP") and was I believe unintentional. This patch has no impact on the case where allocating a pid fails because the child reaper for the namespace is dead; that case will still return -ENOMEM. Link: http://lkml.kernel.org/r/20180903111016.46461-1-ktsanaktsidis@zendesk.com Fixes: 95846ecf9dac ("pid: replace pid bitmap implementation with IDR AIP") Signed-off-by: KJ Tsanaktsidis <ktsanaktsidis@zendesk.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Gargi Sharma <gs051095@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* pid: Implement PIDTYPE_TGIDEric W. Biederman2018-07-211-2/+0
| | | | | | | | | | | | | | | | | | | | | | Everywhere except in the pid array we distinguish between a tasks pid and a tasks tgid (thread group id). Even in the enumeration we want that distinction sometimes so we have added __PIDTYPE_TGID. With leader_pid we almost have an implementation of PIDTYPE_TGID in struct signal_struct. Add PIDTYPE_TGID as a first class member of the pid_type enumeration and into the pids array. Then remove the __PIDTYPE_TGID special case and the leader_pid in signal_struct. The net size increase is just an extra pointer added to struct pid and an extra pair of pointers of an hlist_node added to task_struct. The effect on code maintenance is the removal of a number of special cases today and the potential to remove many more special cases as PIDTYPE_TGID gets used to it's fullest. The long term potential is allowing zombie thread group leaders to exit, which will remove a lot more special cases in the code. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
* pids: Move the pgrp and session pid pointers from task_struct to signal_structEric W. Biederman2018-07-211-23/+22
| | | | | | | | | | | | To access these fields the code always has to go to group leader so going to signal struct is no loss and is actually a fundamental simplification. This saves a little bit of memory by only allocating the pid pointer array once instead of once for every thread, and even better this removes a few potential races caused by the fact that group_leader can be changed by de_thread, while signal_struct can not. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
* pids: Compute task_tgid using signal->leader_pidEric W. Biederman2018-07-211-7/+8
| | | | | | | | | | The cost is the the same and this removes the need to worry about complications that come from de_thread and group_leader changing. __task_pid_nr_ns has been updated to take advantage of this change. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
* xarray: add the xa_lock to the radix_tree_rootMatthew Wilcox2018-04-111-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | This results in no change in structure size on 64-bit machines as it fits in the padding between the gfp_t and the void *. 32-bit machines will grow the structure from 8 to 12 bytes. Almost all radix trees are protected with (at least) a spinlock, so as they are converted from radix trees to xarrays, the data structures will shrink again. Initialising the spinlock requires a name for the benefit of lockdep, so RADIX_TREE_INIT() now needs to know the name of the radix tree it's initialising, and so do IDR_INIT() and IDA_INIT(). Also add the xa_lock() and xa_unlock() family of wrappers to make it easier to use the lock. If we could rely on -fplan9-extensions in the compiler, we could avoid all of this syntactic sugar, but that wasn't added until gcc 4.6. Link: http://lkml.kernel.org/r/20180313132639.17387-8-willy@infradead.org Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* pids: introduce find_get_task_by_vpid() helperMike Rapoport2018-02-061-0/+13
| | | | | | | | | | | There are several functions that do find_task_by_vpid() followed by get_task_struct(). We can use a helper function instead. Link: http://lkml.kernel.org/r/1509602027-11337-1-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge tag 'init_task-20180117' of ↵Linus Torvalds2018-01-291-1/+13
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs Pull init_task initializer cleanups from David Howells: "It doesn't seem useful to have the init_task in a header file rather than in a normal source file. We could consolidate init_task handling instead and expand out various macros. Here's a series of patches that consolidate init_task handling: (1) Make THREAD_SIZE available to vmlinux.lds for cris, hexagon and openrisc. (2) Alter the INIT_TASK_DATA linker script macro to set init_thread_union and init_stack rather than defining these in C. Insert init_task and init_thread_into into the init_stack area in the linker script as appropriate to the configuration, with different section markers so that they end up correctly ordered. We can then get merge ia64's init_task.c into the main one. We then have a bunch of single-use INIT_*() macros that seem only to be macros because they used to be used per-arch. We can then expand these in place of the user and get rid of a few lines and a lot of backslashes. (3) Expand INIT_TASK() in place. (4) Expand in place various small INIT_*() macros that are defined conditionally. Expand them and surround them by #if[n]def/#endif in the .c file as it takes fewer lines. (5) Expand INIT_SIGNALS() and INIT_SIGHAND() in place. (6) Expand INIT_STRUCT_PID in place. These macros can then be discarded" * tag 'init_task-20180117' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs: Expand INIT_STRUCT_PID and remove Expand the INIT_SIGNALS and INIT_SIGHAND macros and remove Expand various INIT_* macros and remove Expand INIT_TASK() in init/init_task.c and remove Construct init thread stack in the linker script rather than by union openrisc: Make THREAD_SIZE available to vmlinux.lds hexagon: Make THREAD_SIZE available to vmlinux.lds cris: Make THREAD_SIZE available to vmlinux.lds
| * Expand INIT_STRUCT_PID and removeDavid Howells2018-01-171-1/+13
| | | | | | | | | | | | | | | | | | | | | | Expand INIT_STRUCT_PID in the single place that uses it and then remove it. There doesn't seem any point in the macro. Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Tony Luck <tony.luck@intel.com> Tested-by: Will Deacon <will.deacon@arm.com> (arm64) Tested-by: Palmer Dabbelt <palmer@sifive.com> Acked-by: Thomas Gleixner <tglx@linutronix.de>
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-19 00:09:41 +0000