Commit 59647b6a authored by Thomas Gleixner's avatar Thomas Gleixner

futex: Handle futex value corruption gracefully

The WARN_ON in lookup_pi_state which complains about a mismatch
between pi_state->owner->pid and the pid which we retrieved from the
user space futex is completely bogus.

The code just emits the warning and then continues despite the fact
that it detected an inconsistent state of the futex. A conveniant way
for user space to spam the syslog.

Replace the WARN_ON by a consistency check. If the values do not match
return -EINVAL and let user space deal with the mess it created.

This also fixes the missing task_pid_vnr() when we compare the
pi_state->owner pid with the futex value.
Reported-by: default avatarJermome Marchand <jmarchan@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarDarren Hart <dvhltc@us.ibm.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
parent 51246bfd
......@@ -530,8 +530,25 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
return -EINVAL;
WARN_ON(!atomic_read(&pi_state->refcount));
WARN_ON(pid && pi_state->owner &&
pi_state->owner->pid != pid);
/*
* When pi_state->owner is NULL then the owner died
* and another waiter is on the fly. pi_state->owner
* is fixed up by the task which acquires
* pi_state->rt_mutex.
*
* We do not check for pid == 0 which can happen when
* the owner died and robust_list_exit() cleared the
* TID.
*/
if (pid && pi_state->owner) {
/*
* Bail out if user space manipulated the
* futex value.
*/
if (pid != task_pid_vnr(pi_state->owner))
return -EINVAL;
}
atomic_inc(&pi_state->refcount);
*ps = pi_state;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment