@@ -2373,8 +2373,8 @@ retry:
}
if (__rt_mutex_futex_trylock(&pi_state->pi_mutex)) {
- /* We got the lock after all, nothing to fix. */
- ret = 0;
+ /* We got the lock. pi_state is correct. Tell caller. */
+ ret = 1;
goto out_unlock;
}
@@ -2402,7 +2402,7 @@ retry:
* We raced against a concurrent self; things are
* already fixed up. Nothing to do.
*/
- ret = 0;
+ ret = 1;
goto out_unlock;
}
newowner = argowner;
@@ -2448,7 +2448,7 @@ retry:
raw_spin_unlock(&newowner->pi_lock);
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
- return 0;
+ return argowner == current;
/*
* In order to reschedule or handle a page fault, we need to drop the
@@ -2490,7 +2490,7 @@ handle_err:
* Check if someone else fixed it for us:
*/
if (pi_state->owner != oldowner) {
- ret = 0;
+ ret = argowner == current;
goto out_unlock;
}
@@ -2523,8 +2523,6 @@ static long futex_wait_restart(struct restart_block *restart);
*/
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
@@ -2535,8 +2533,8 @@ static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
* stable state, anything else needs more attention.
*/
if (q->pi_state->owner != current)
- ret = fixup_pi_state_owner(uaddr, q, current);
- return ret ? ret : locked;
+ return fixup_pi_state_owner(uaddr, q, current);
+ return 1;
}
/*
@@ -2547,10 +2545,8 @@ static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
* 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);
- return ret;
- }
+ 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
@@ -2563,7 +2559,7 @@ static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
q->pi_state->owner);
}
- return ret;
+ return 0;
}
/**
@@ -3261,7 +3257,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
if (q.pi_state && (q.pi_state->owner != current)) {
spin_lock(q.lock_ptr);
ret = fixup_pi_state_owner(uaddr2, &q, current);
- if (ret && rt_mutex_owner(&q.pi_state->pi_mutex) == current) {
+ if (ret < 0 && rt_mutex_owner(&q.pi_state->pi_mutex) == current) {
pi_state = q.pi_state;
get_pi_state(pi_state);
}
@@ -3271,6 +3267,11 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
*/
put_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;
The following commit has been merged into the locking/urgent branch of tip: Commit-ID: 12bb3f7f1b03d5913b3f9d4236a488aa7774dfe9 Gitweb: https://git.kernel.org/tip/12bb3f7f1b03d5913b3f9d4236a488aa7774dfe9 Author: Thomas Gleixner <tglx@linutronix.de> AuthorDate: Wed, 20 Jan 2021 16:00:24 +01:00 Committer: Thomas Gleixner <tglx@linutronix.de> CommitterDate: Tue, 26 Jan 2021 15:10:58 +01:00 futex: Ensure the correct return value from futex_lock_pi() 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 <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: stable@vger.kernel.org --- kernel/futex.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-)