This is a note to let you know that I've just added the patch titled futex: Fix incorrect should_fail_futex() handling to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: futex-fix-incorrect-should_fail_futex-handling.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit bfc3326dea642b2183c4f0bb6b9e209ad83e4745 Author: Mateusz Nosek <mateusznosek0@xxxxxxxxx> Date: Sun Sep 27 02:08:58 2020 +0200 futex: Fix incorrect should_fail_futex() handling [ Upstream commit 921c7ebd1337d1a46783d7e15a850e12aed2eaa0 ] 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: 6b4f4bc9cb22 ("locking/futex: Allow low-level atomic operations to return -EAGAIN") Signed-off-by: Mateusz Nosek <mateusznosek0@xxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20200927000858.24219-1-mateusznosek0@xxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/futex.c b/kernel/futex.c index a5876694a60eb..39681bf8b06ca 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -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)) {