This is a note to let you know that I've just added the patch titled
futex: Always cleanup owner tid in unlock_pi
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
futex-always-cleanup-owner-tid-in-unlock_pi.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 13fbca4c6ecd96ec1a1cfa2e4f2ce191fe928a5e Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <[email protected]>
Date: Tue, 3 Jun 2014 12:27:07 +0000
Subject: futex: Always cleanup owner tid in unlock_pi
From: Thomas Gleixner <[email protected]>
commit 13fbca4c6ecd96ec1a1cfa2e4f2ce191fe928a5e upstream.
If the owner died bit is set at futex_unlock_pi, we currently do not
cleanup the user space futex. So the owner TID of the current owner
(the unlocker) persists. That's observable inconsistant state,
especially when the ownership of the pi state got transferred.
Clean it up unconditionally.
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Will Drewry <[email protected]>
Cc: Darren Hart <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/futex.c | 44 ++++++++++++++++++++------------------------
1 file changed, 20 insertions(+), 24 deletions(-)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -899,6 +899,7 @@ static int wake_futex_pi(u32 __user *uad
struct task_struct *new_owner;
struct futex_pi_state *pi_state = this->pi_state;
u32 uninitialized_var(curval), newval;
+ int ret = 0;
if (!pi_state)
return -EINVAL;
@@ -922,23 +923,19 @@ static int wake_futex_pi(u32 __user *uad
new_owner = this->task;
/*
- * We pass it to the next owner. (The WAITERS bit is always
- * kept enabled while there is PI state around. We must also
- * preserve the owner died bit.)
- */
- if (!(uval & FUTEX_OWNER_DIED)) {
- int ret = 0;
-
- newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
-
- if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
- ret = -EFAULT;
- else if (curval != uval)
- ret = -EINVAL;
- if (ret) {
- raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
- return ret;
- }
+ * We pass it to the next owner. The WAITERS bit is always
+ * kept enabled while there is PI state around. We cleanup the
+ * owner died bit, because we are the owner.
+ */
+ newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
+
+ if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
+ ret = -EFAULT;
+ else if (curval != uval)
+ ret = -EINVAL;
+ if (ret) {
+ raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
+ return ret;
}
raw_spin_lock_irq(&pi_state->owner->pi_lock);
@@ -2183,9 +2180,10 @@ retry:
/*
* To avoid races, try to do the TID -> 0 atomic transition
* again. If it succeeds then we can return without waking
- * anyone else up:
+ * anyone else up. We only try this if neither the waiters nor
+ * the owner died bit are set.
*/
- if (!(uval & FUTEX_OWNER_DIED) &&
+ if (!(uval & ~FUTEX_TID_MASK) &&
cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0))
goto pi_faulted;
/*
@@ -2217,11 +2215,9 @@ retry:
/*
* No waiters - kernel unlocks the futex:
*/
- if (!(uval & FUTEX_OWNER_DIED)) {
- ret = unlock_futex_pi(uaddr, uval);
- if (ret == -EFAULT)
- goto pi_faulted;
- }
+ ret = unlock_futex_pi(uaddr, uval);
+ if (ret == -EFAULT)
+ goto pi_faulted;
out_unlock:
spin_unlock(&hb->lock);
Patches currently in stable-queue which might be from [email protected] are
queue-3.4/futex-always-cleanup-owner-tid-in-unlock_pi.patch
queue-3.4/futex-prevent-requeue-pi-on-same-futex.patch-futex-forbid-uaddr-uaddr2-in-futex_requeue-...-requeue_pi-1.patch
queue-3.4/futex-validate-atomic-acquisition-in-futex_lock_pi_atomic.patch
queue-3.4/futex-add-another-early-deadlock-detection-check.patch
queue-3.4/futex-make-lookup_pi_state-more-robust.patch
queue-3.4/futex-prevent-attaching-to-kernel-threads.patch
queue-3.4/hrtimer-prevent-all-reprogramming-if-hang-detected.patch
queue-3.4/hrtimer-prevent-remote-enqueue-of-leftmost-timers.patch
queue-3.4/hrtimer-set-expiry-time-before-switch_hrtimer_base.patch
queue-3.4/timer-prevent-overflow-in-apply_slack.patch
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