Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=179394af7a2baa1d0a3cb1670075310d72247d38
Commit: 179394af7a2baa1d0a3cb1670075310d72247d38
Parent: 928923c76b393e38e5ba1d47e843e208ceef6cf9
Author: Thomas Gleixner <[EMAIL PROTECTED]>
AuthorDate: Wed Aug 22 14:01:37 2007 -0700
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Aug 22 19:52:45 2007 -0700
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 <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
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 55b3761..6923ad8 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);
-
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