From: Eslam Khafagy Date: Fri, 14 Nov 2025 12:27:39 +0000 (+0200) Subject: posix-timers: Plug potential memory leak in do_timer_create() X-Git-Tag: v6.18-rc6~7^2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e0fd4d42e27f761e9cc82801b3f183e658dc749d;p=thirdparty%2Flinux.git posix-timers: Plug potential memory leak in do_timer_create() When posix timer creation is set to allocate a given timer ID and the access to the user space value faults, the function terminates without freeing the already allocated posix timer structure. Move the allocation after the user space access to cure that. [ tglx: Massaged change log ] Fixes: ec2d0c04624b3 ("posix-timers: Provide a mechanism to allocate a given timer ID") Reported-by: syzbot+9c47ad18f978d4394986@syzkaller.appspotmail.com Suggested-by: Cyrill Gorcunov Signed-off-by: Eslam Khafagy Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://patch.msgid.link/20251114122739.994326-1-eslam.medhat1993@gmail.com Closes: https://lore.kernel.org/all/69155df4.a70a0220.3124cb.0017.GAE@google.com/T/ --- diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c index aa3120104a512..56e17b625c72e 100644 --- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -475,12 +475,6 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, if (!kc->timer_create) return -EOPNOTSUPP; - new_timer = alloc_posix_timer(); - if (unlikely(!new_timer)) - return -EAGAIN; - - spin_lock_init(&new_timer->it_lock); - /* Special case for CRIU to restore timers with a given timer ID. */ if (unlikely(current->signal->timer_create_restore_ids)) { if (copy_from_user(&req_id, created_timer_id, sizeof(req_id))) @@ -490,6 +484,12 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event, return -EINVAL; } + new_timer = alloc_posix_timer(); + if (unlikely(!new_timer)) + return -EAGAIN; + + spin_lock_init(&new_timer->it_lock); + /* * Add the timer to the hash table. The timer is not yet valid * after insertion, but has a unique ID allocated.