taskstats: fix data-race
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 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 READ_ONCE() and smp_store_release().
Reported-by: syzbot+c5d03165a1bd1dead0c1@syzkaller.appspotmail.com
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20191006235216.7483-1-christian.brauner@ubuntu.com
---
/* v1 */
Link: https://lore.kernel.org/r/20191005112806.13960-1-christian.brauner@ubuntu.com
/* v2 */
- Dmitry Vyukov <dvyukov@google.com>, Marco Elver <elver@google.com>:
- fix the original double-checked locking using memory barriers
1 file changed
