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author | Christian Brauner <christian.brauner@ubuntu.com> | 2020-05-31 13:50:29 +0200 |
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committer | Kees Cook <keescook@chromium.org> | 2020-07-10 16:01:51 -0700 |
commit | 3a15fb6ed92cb32b0a83f406aa4a96f28c9adbc3 (patch) | |
tree | 3ca1c281e1a283385214bd49eaa0c3e4a33330b5 /kernel/exit.c | |
parent | b707ddee11d1dc4518ab7f1aa5e7af9ceaa23317 (diff) | |
download | linux-3a15fb6ed92cb32b0a83f406aa4a96f28c9adbc3.tar.gz linux-3a15fb6ed92cb32b0a83f406aa4a96f28c9adbc3.tar.bz2 linux-3a15fb6ed92cb32b0a83f406aa4a96f28c9adbc3.zip |
seccomp: release filter after task is fully dead
The seccomp filter used to be released in free_task() which is called
asynchronously via call_rcu() and assorted mechanisms. Since we need
to inform tasks waiting on the seccomp notifier when a filter goes empty
we will notify them as soon as a task has been marked fully dead in
release_task(). To not split seccomp cleanup into two parts, move
filter release out of free_task() and into release_task() after we've
unhashed struct task from struct pid, exited signals, and unlinked it
from the threadgroups' thread list. We'll put the empty filter
notification infrastructure into it in a follow up patch.
This also renames put_seccomp_filter() to seccomp_filter_release() which
is a more descriptive name of what we're doing here especially once
we've added the empty filter notification mechanism in there.
We're also NULL-ing the task's filter tree entrypoint which seems
cleaner than leaving a dangling pointer in there. Note that this shouldn't
need any memory barriers since we're calling this when the task is in
release_task() which means it's EXIT_DEAD. So it can't modify its seccomp
filters anymore. You can also see this from the point where we're calling
seccomp_filter_release(). It's after __exit_signal() and at this point,
tsk->sighand will already have been NULLed which is required for
thread-sync and filter installation alike.
Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matt Denton <mpdenton@google.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Jann Horn <jannh@google.com>
Cc: Chris Palmer <palmer@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Robert Sesek <rsesek@google.com>
Cc: Jeffrey Vander Stoep <jeffv@google.com>
Cc: Linux Containers <containers@lists.linux-foundation.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20200531115031.391515-2-christian.brauner@ubuntu.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r-- | kernel/exit.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 727150f28103..00d77e5ba700 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -217,6 +217,7 @@ repeat: } write_unlock_irq(&tasklist_lock); + seccomp_filter_release(p); proc_flush_pid(thread_pid); put_pid(thread_pid); release_thread(p); |