The following commit has been merged into the timers/urgent branch of tip:
Commit-ID: e362359ace6f87c201531872486ff295df306d13 Gitweb: https://git.kernel.org/tip/e362359ace6f87c201531872486ff295df306d13 Author: Thadeu Lima de Souza Cascardo cascardo@canonical.com AuthorDate: Tue, 09 Aug 2022 14:07:51 -03:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Tue, 09 Aug 2022 20:02:13 +02:00
posix-cpu-timers: Cleanup CPU timers before freeing them during exec
Commit 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task") started looking up tasks by PID when deleting a CPU timer.
When a non-leader thread calls execve, it will switch PIDs with the leader process. Then, as it calls exit_itimers, posix_cpu_timer_del cannot find the task because the timer still points out to the old PID.
That means that armed timers won't be disarmed, that is, they won't be removed from the timerqueue_list. exit_itimers will still release their memory, and when that list is later processed, it leads to a use-after-free.
Clean up the timers from the de-threaded task before freeing them. This prevents a reported use-after-free.
Fixes: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task") Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220809170751.164716-1-cascardo@canonical.com
--- fs/exec.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/exec.c b/fs/exec.c index 5fd7391..f793221 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1304,6 +1304,9 @@ int begin_new_exec(struct linux_binprm * bprm) bprm->mm = NULL;
#ifdef CONFIG_POSIX_TIMERS + spin_lock_irq(&me->sighand->siglock); + posix_cpu_timers_exit(me); + spin_unlock_irq(&me->sighand->siglock); exit_itimers(me); flush_itimer_signals(); #endif