From 541840859ace9c2ccebc32fa9e376c7bd3def490 Mon Sep 17 00:00:00 2001 From: Thadeu Lima de Souza Cascardo Date: Tue, 9 Aug 2022 14:07:51 -0300 Subject: posix-cpu-timers: Cleanup CPU timers before freeing them during exec commit e362359ace6f87c201531872486ff295df306d13 upstream. 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 Signed-off-by: Thomas Gleixner Reviewed-by: Thomas Gleixner Cc: Link: https://lore.kernel.org/r/20220809170751.164716-1-cascardo@canonical.com Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs') diff --git a/fs/exec.c b/fs/exec.c index d37a82206fa3..b56bc4b4016e 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1286,6 +1286,9 @@ 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 -- cgit v1.2.3