Re: FAILED: patch "[PATCH] futex/requeue: Prevent NULL pointer dereference in" failed to apply to 5.10-stable tree

[Thomas Gleixner <tglx@kernel.org>]

On Tue, Jul 21 2026 at 17:13, gregkh@linuxfoundation.org wrote:
> The patch below does not apply to the 5.10-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
>
> To reproduce the conflict and resubmit, you may use the following commands:
>
> git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
> git checkout FETCH_HEAD
> git cherry-pick -x 74e144274af39935b0f410c0ee4d2b91c3730414

As I said before this commit should not be backported as it is buggy and
got reverted upstream:

  39def6d250d3 ("futex/requeue: Revert "Prevent NULL pointer dereference in remove_waiter() on self-deadlock""")

The one which fixes the actual problem is:

   40a25d59e85b ("locking/rtmutex: Skip remove_waiter() when waiter is not enqueued")

That one does not apply to 5.10/15 either as the prerequisite

    3bfdc63936dd ("rtmutex: Use waiter::task instead of current in remove_waiter()")

has not been backported presumably because the Fixes tag in that commit
points to a commit which got introduced post 5.15. Though the bug it
fixes got introduced way earlier.

Let me backport these two:

   3bfdc63936dd ("rtmutex: Use waiter::task instead of current in remove_waiter()")
   40a25d59e85b ("locking/rtmutex: Skip remove_waiter() when waiter is not enqueued")

to 5.10.y and 5.15.y. I'll send a series later.

Thanks,

        tglx