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author | Thomas Gleixner <tglx@linutronix.de> | 2007-08-22 14:01:37 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-08-22 19:52:45 -0700 |
commit | 179394af7a2baa1d0a3cb1670075310d72247d38 (patch) | |
tree | f15d4ad366b1bfa7787d6a6a809816f507c4a23a /kernel/posix-timers.c | |
parent | 928923c76b393e38e5ba1d47e843e208ceef6cf9 (diff) | |
download | linux-stable-179394af7a2baa1d0a3cb1670075310d72247d38.tar.gz linux-stable-179394af7a2baa1d0a3cb1670075310d72247d38.tar.bz2 linux-stable-179394af7a2baa1d0a3cb1670075310d72247d38.zip |
posix-timers: fix deletion race
timer_delete does:
lock_timer();
timer->it_process = NULL;
unlock_timer();
release_posix_timer();
timer->it_process is checked in lock_timer() to prevent access to a
timer, which is on the way to be deleted, but the check happens after
idr_lock is dropped. This allows release_posix_timer() to delete the
timer before the lock code can check the timer:
CPU 0 CPU 1
lock_timer();
timer->it_process = NULL;
unlock_timer();
lock_timer()
spin_lock(idr_lock);
timer = idr_find();
spin_lock(timer->lock);
spin_unlock(idr_lock);
release_posix_timer();
spin_lock(idr_lock);
idr_remove(timer);
spin_unlock(idr_lock);
free_timer(timer);
if (timer->......)
Change the locking to prevent this.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/posix-timers.c')
-rw-r--r-- | kernel/posix-timers.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c index 55b3761edaa9..6923ad8a5983 100644 --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -605,13 +605,14 @@ static struct k_itimer * lock_timer(timer_t timer_id, unsigned long *flags) timr = (struct k_itimer *) idr_find(&posix_timers_id, (int) timer_id); if (timr) { spin_lock(&timr->it_lock); - spin_unlock(&idr_lock); if ((timr->it_id != timer_id) || !(timr->it_process) || timr->it_process->tgid != current->tgid) { - unlock_timer(timr, *flags); + spin_unlock(&timr->it_lock); + spin_unlock_irqrestore(&idr_lock, *flags); timr = NULL; - } + } else + spin_unlock(&idr_lock); } else spin_unlock_irqrestore(&idr_lock, *flags); |