On Wed, Oct 09, 2019 at 01:48:09PM +0200, Christian Brauner wrote:
When assiging and testing taskstats in taskstats_exit() there's a race when writing and reading sig->stats when a thread-group with more than one thread exits:
cpu0: thread catches fatal signal and whole thread-group gets taken down do_exit() do_group_exit() taskstats_exit() taskstats_tgid_alloc() The tasks reads sig->stats without holding sighand lock seeing garbage.
cpu1: task calls exit_group() do_exit() do_group_exit() taskstats_exit() taskstats_tgid_alloc() The task takes sighand lock and assigns new stats to sig->stats.
Fix this by using smp_load_acquire() and smp_store_release().
Reported-by: syzbot+c5d03165a1bd1dead0c1@syzkaller.appspotmail.com Fixes: 34ec12349c8a ("taskstats: cleanup ->signal->stats allocation") Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner christian.brauner@ubuntu.com Reviewed-by: Dmitry Vyukov dvyukov@google.com
Applied to: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=tas...
Merged into: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=fix...
Targeting v5.4-rc3.
Thanks! Christian