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futex: Fix incorrect should_fail_futex() handling 

If should_futex_fail() returns true in futex_wake_pi(), then the 'ret'
variable is set to -EFAULT and then immediately overwritten. So the failure
injection is non-functional.

Fix it by actually leaving the function and returning -EFAULT.

The Fixes tag is kinda blury because the initial commit which introduced
failure injection was already sloppy, but the below mentioned commit broke
it completely.

[ tglx: Massaged changelog ]

Fixes: 6b4f4bc9cb ("locking/futex: Allow low-level atomic operations to return -EAGAIN")
Signed-off-by: Mateusz Nosek <mateusznosek0@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200927000858.24219-1-mateusznosek0@gmail.com
This commit is contained in:
Mateusz Nosek 2020-09-27 02:08:58 +02:00 committed by Thomas Gleixner
parent f8e48a3dca
commit 921c7ebd13
1 changed files with 3 additions and 1 deletions
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4
kernel/futex.c
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@ -1502,8 +1502,10 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_
*/
newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
if (unlikely(should_fail_futex(true)))
if (unlikely(should_fail_futex(true))) {
ret = -EFAULT;
goto out_unlock;
}
ret = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
if (!ret && (curval != uval)) {