Commit 921c7ebd authored Sep 27, 2020 by Mateusz Nosek Committed by Thomas Gleixner Oct 28, 2020

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: 6b4f4bc9 ("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

parent f8e48a3d

kernel/futex.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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)) {

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