From: Thomas Gleixner <t...@linutronix.de>
commit 12bb3f7f1b03d5913b3f9d4236a488aa7774dfe9 upstream.
In case that futex_lock_pi() was aborted by a signal or a timeout and the
task returned without acquiring the rtmutex, but is the designated owner of
the futex due to a concurrent futex_unlock_pi() fixup_owner() is invoked to
establish consistent state. In that case it invokes fixup_pi_state_owner()
which in turn tries to acquire the rtmutex again. If that succeeds then it
does not propagate this success to fixup_owner() and futex_lock_pi()
returns -EINTR or -ETIMEOUT despite having the futex locked.
Return success from fixup_pi_state_owner() in all cases where the current
task owns the rtmutex and therefore the futex and propagate it correctly
through fixup_owner(). Fixup the other callsite which does not expect a
positive return value.
Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
[Sharan: Backported patch for kernel 4.4.y. Also folded in is a part
of the cleanup patch d7c5ed73b19c("futex: Remove needless goto's")]
Signed-off-by: Sharan Turlapati <sturlap...@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
kernel/futex.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2283,7 +2283,7 @@ retry:
}
if (__rt_mutex_futex_trylock(&pi_state->pi_mutex)) {
- /* We got the lock after all, nothing to fix. */
+ /* We got the lock. pi_state is correct. Tell caller */
return 1;
}
@@ -2328,7 +2328,7 @@ retry:
*/
pi_state_update_owner(pi_state, newowner);
- return 0;
+ return argowner == current;
/*
* To handle the page fault we need to drop the hash bucket
@@ -2411,8 +2411,6 @@ static long futex_wait_restart(struct re
*/
static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
{
- int ret = 0;
-
if (locked) {
/*
* Got the lock. We might not be the anticipated owner if we
@@ -2423,8 +2421,8 @@ static int fixup_owner(u32 __user *uaddr
* stable state, anything else needs more attention.
*/
if (q->pi_state->owner != current)
- ret = fixup_pi_state_owner(uaddr, q, current);
- goto out;
+ return fixup_pi_state_owner(uaddr, q, current);
+ return 1;
}
/*
@@ -2435,10 +2433,8 @@ static int fixup_owner(u32 __user *uaddr
* Another speculative read; pi_state->owner == current is unstable
* but needs our attention.
*/
- if (q->pi_state->owner == current) {
- ret = fixup_pi_state_owner(uaddr, q, NULL);
- goto out;
- }
+ if (q->pi_state->owner == current)
+ return fixup_pi_state_owner(uaddr, q, NULL);
/*
* Paranoia check. If we did not take the lock, then we should not be
@@ -2447,8 +2443,7 @@ static int fixup_owner(u32 __user *uaddr
if (WARN_ON_ONCE(rt_mutex_owner(&q->pi_state->pi_mutex) == current))
return fixup_pi_state_owner(uaddr, q, current);
-out:
- return ret ? ret : locked;
+ return 0;
}
/**
@@ -3070,6 +3065,11 @@ static int futex_wait_requeue_pi(u32 __u
*/
free_pi_state(q.pi_state);
spin_unlock(q.lock_ptr);
+ /*
+ * Adjust the return value. It's either -EFAULT or
+ * success (1) but the caller expects 0 for success.
+ */
+ ret = ret < 0 ? ret : 0;
}
} else {
struct rt_mutex *pi_mutex;
