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authorChristian Brauner <christian.brauner@ubuntu.com>2020-05-31 13:50:29 +0200
committerKees Cook <keescook@chromium.org>2020-07-10 16:01:51 -0700
commit3a15fb6ed92cb32b0a83f406aa4a96f28c9adbc3 (patch)
tree3ca1c281e1a283385214bd49eaa0c3e4a33330b5 /kernel/exit.c
parentb707ddee11d1dc4518ab7f1aa5e7af9ceaa23317 (diff)
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.c1
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);