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futex: Ensure the correct return value from futex_lock_pi()

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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 <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[Lee: Back-ported in support of a previous futex attempt]
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Gleixner 2021-02-11 09:26:58 +00:00 committed by Greg Kroah-Hartman
parent aff8214636
commit ad8fdbabcc
1 changed files with 12 additions and 12 deletions
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24
kernel/futex.c
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@ -2322,7 +2322,7 @@ 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;
}
@ -2364,7 +2364,7 @@ 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
@ -2447,8 +2447,6 @@ 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
@ -2459,8 +2457,8 @@ 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);
goto out;
return fixup_pi_state_owner(uaddr, q, current);
return 1;
}
/*
@ -2471,10 +2469,8 @@ 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);
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
@ -2483,8 +2479,7 @@ static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
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;
}
/**
@ -3106,6 +3101,11 @@ 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;