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authorLinus Torvalds <torvalds@linux-foundation.org>2022-01-17 05:49:30 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2022-01-17 05:49:30 +0200
commit35ce8ae9ae2e471f92759f9d6880eab42cc1c3b6 (patch)
treed6299a6010d1d88c1ab93f406c0a392e3aaa919e /kernel/kthread.c
parent6661224e66f03706daea8e27714436851cf01731 (diff)
parenta403df29789ba38796edb97dad9bfb47836b68c0 (diff)
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Merge branch 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull signal/exit/ptrace updates from Eric Biederman: "This set of changes deletes some dead code, makes a lot of cleanups which hopefully make the code easier to follow, and fixes bugs found along the way. The end-game which I have not yet reached yet is for fatal signals that generate coredumps to be short-circuit deliverable from complete_signal, for force_siginfo_to_task not to require changing userspace configured signal delivery state, and for the ptrace stops to always happen in locations where we can guarantee on all architectures that the all of the registers are saved and available on the stack. Removal of profile_task_ext, profile_munmap, and profile_handoff_task are the big successes for dead code removal this round. A bunch of small bug fixes are included, as most of the issues reported were small enough that they would not affect bisection so I simply added the fixes and did not fold the fixes into the changes they were fixing. There was a bug that broke coredumps piped to systemd-coredump. I dropped the change that caused that bug and replaced it entirely with something much more restrained. Unfortunately that required some rebasing. Some successes after this set of changes: There are few enough calls to do_exit to audit in a reasonable amount of time. The lifetime of struct kthread now matches the lifetime of struct task, and the pointer to struct kthread is no longer stored in set_child_tid. The flag SIGNAL_GROUP_COREDUMP is removed. The field group_exit_task is removed. Issues where task->exit_code was examined with signal->group_exit_code should been examined were fixed. There are several loosely related changes included because I am cleaning up and if I don't include them they will probably get lost. The original postings of these changes can be found at: https://lkml.kernel.org/r/87a6ha4zsd.fsf@email.froward.int.ebiederm.org https://lkml.kernel.org/r/87bl1kunjj.fsf@email.froward.int.ebiederm.org https://lkml.kernel.org/r/87r19opkx1.fsf_-_@email.froward.int.ebiederm.org I trimmed back the last set of changes to only the obviously correct once. Simply because there was less time for review than I had hoped" * 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (44 commits) ptrace/m68k: Stop open coding ptrace_report_syscall ptrace: Remove unused regs argument from ptrace_report_syscall ptrace: Remove second setting of PT_SEIZED in ptrace_attach taskstats: Cleanup the use of task->exit_code exit: Use the correct exit_code in /proc/<pid>/stat exit: Fix the exit_code for wait_task_zombie exit: Coredumps reach do_group_exit exit: Remove profile_handoff_task exit: Remove profile_task_exit & profile_munmap signal: clean up kernel-doc comments signal: Remove the helper signal_group_exit signal: Rename group_exit_task group_exec_task coredump: Stop setting signal->group_exit_task signal: Remove SIGNAL_GROUP_COREDUMP signal: During coredumps set SIGNAL_GROUP_EXIT in zap_process signal: Make coredump handling explicit in complete_signal signal: Have prepare_signal detect coredumps using signal->core_state signal: Have the oom killer detect coredumps using signal->core_state exit: Move force_uaccess back into do_exit exit: Guarantee make_task_dead leaks the tsk when calling do_task_exit ...
Diffstat (limited to 'kernel/kthread.c')
-rw-r--r--kernel/kthread.c88
1 files changed, 60 insertions, 28 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 4ed9e7bce9e8..a2c156ee8275 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -52,6 +52,7 @@ struct kthread_create_info
struct kthread {
unsigned long flags;
unsigned int cpu;
+ int result;
int (*threadfn)(void *);
void *data;
mm_segment_t oldfs;
@@ -71,7 +72,7 @@ enum KTHREAD_BITS {
static inline struct kthread *to_kthread(struct task_struct *k)
{
WARN_ON(!(k->flags & PF_KTHREAD));
- return (__force void *)k->set_child_tid;
+ return k->worker_private;
}
/*
@@ -79,7 +80,7 @@ static inline struct kthread *to_kthread(struct task_struct *k)
*
* Per construction; when:
*
- * (p->flags & PF_KTHREAD) && p->set_child_tid
+ * (p->flags & PF_KTHREAD) && p->worker_private
*
* the task is both a kthread and struct kthread is persistent. However
* PF_KTHREAD on it's own is not, kernel_thread() can exec() (See umh.c and
@@ -87,26 +88,29 @@ static inline struct kthread *to_kthread(struct task_struct *k)
*/
static inline struct kthread *__to_kthread(struct task_struct *p)
{
- void *kthread = (__force void *)p->set_child_tid;
+ void *kthread = p->worker_private;
if (kthread && !(p->flags & PF_KTHREAD))
kthread = NULL;
return kthread;
}
-void set_kthread_struct(struct task_struct *p)
+bool set_kthread_struct(struct task_struct *p)
{
struct kthread *kthread;
- if (__to_kthread(p))
- return;
+ if (WARN_ON_ONCE(to_kthread(p)))
+ return false;
kthread = kzalloc(sizeof(*kthread), GFP_KERNEL);
- /*
- * We abuse ->set_child_tid to avoid the new member and because it
- * can't be wrongly copied by copy_process(). We also rely on fact
- * that the caller can't exec, so PF_KTHREAD can't be cleared.
- */
- p->set_child_tid = (__force void __user *)kthread;
+ if (!kthread)
+ return false;
+
+ init_completion(&kthread->exited);
+ init_completion(&kthread->parked);
+ p->vfork_done = &kthread->exited;
+
+ p->worker_private = kthread;
+ return true;
}
void free_kthread_struct(struct task_struct *k)
@@ -114,13 +118,13 @@ void free_kthread_struct(struct task_struct *k)
struct kthread *kthread;
/*
- * Can be NULL if this kthread was created by kernel_thread()
- * or if kmalloc() in kthread() failed.
+ * Can be NULL if kmalloc() in set_kthread_struct() failed.
*/
kthread = to_kthread(k);
#ifdef CONFIG_BLK_CGROUP
WARN_ON_ONCE(kthread && kthread->blkcg_css);
#endif
+ k->worker_private = NULL;
kfree(kthread);
}
@@ -268,6 +272,44 @@ void kthread_parkme(void)
}
EXPORT_SYMBOL_GPL(kthread_parkme);
+/**
+ * kthread_exit - Cause the current kthread return @result to kthread_stop().
+ * @result: The integer value to return to kthread_stop().
+ *
+ * While kthread_exit can be called directly, it exists so that
+ * functions which do some additional work in non-modular code such as
+ * module_put_and_kthread_exit can be implemented.
+ *
+ * Does not return.
+ */
+void __noreturn kthread_exit(long result)
+{
+ struct kthread *kthread = to_kthread(current);
+ kthread->result = result;
+ do_exit(0);
+}
+
+/**
+ * kthread_complete_and_exit - Exit the current kthread.
+ * @comp: Completion to complete
+ * @code: The integer value to return to kthread_stop().
+ *
+ * If present complete @comp and the reuturn code to kthread_stop().
+ *
+ * A kernel thread whose module may be removed after the completion of
+ * @comp can use this function exit safely.
+ *
+ * Does not return.
+ */
+void __noreturn kthread_complete_and_exit(struct completion *comp, long code)
+{
+ if (comp)
+ complete(comp);
+
+ kthread_exit(code);
+}
+EXPORT_SYMBOL(kthread_complete_and_exit);
+
static int kthread(void *_create)
{
static const struct sched_param param = { .sched_priority = 0 };
@@ -279,27 +321,17 @@ static int kthread(void *_create)
struct kthread *self;
int ret;
- set_kthread_struct(current);
self = to_kthread(current);
/* If user was SIGKILLed, I release the structure. */
done = xchg(&create->done, NULL);
if (!done) {
kfree(create);
- do_exit(-EINTR);
- }
-
- if (!self) {
- create->result = ERR_PTR(-ENOMEM);
- complete(done);
- do_exit(-ENOMEM);
+ kthread_exit(-EINTR);
}
self->threadfn = threadfn;
self->data = data;
- init_completion(&self->exited);
- init_completion(&self->parked);
- current->vfork_done = &self->exited;
/*
* The new thread inherited kthreadd's priority and CPU mask. Reset
@@ -326,7 +358,7 @@ static int kthread(void *_create)
__kthread_parkme(self);
ret = threadfn(data);
}
- do_exit(ret);
+ kthread_exit(ret);
}
/* called from kernel_clone() to get node information for about to be created task */
@@ -628,7 +660,7 @@ EXPORT_SYMBOL_GPL(kthread_park);
* instead of calling wake_up_process(): the thread will exit without
* calling threadfn().
*
- * If threadfn() may call do_exit() itself, the caller must ensure
+ * If threadfn() may call kthread_exit() itself, the caller must ensure
* task_struct can't go away.
*
* Returns the result of threadfn(), or %-EINTR if wake_up_process()
@@ -647,7 +679,7 @@ int kthread_stop(struct task_struct *k)
kthread_unpark(k);
wake_up_process(k);
wait_for_completion(&kthread->exited);
- ret = k->exit_code;
+ ret = kthread->result;
put_task_struct(k);
trace_sched_kthread_stop_ret(ret);