Patch "userfaultfd: non-cooperative: flush event_wqh at release time" has been added to the 4.12-stable tree

Patch "userfaultfd: non-cooperative: flush event_wqh at release time" has been added to the 4.12-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    userfaultfd: non-cooperative: flush event_wqh at release time

to the 4.12-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:
     userfaultfd-non-cooperative-flush-event_wqh-at-release-time.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 5a18b64e3f02125be1c0ef777501ae38aafe2a24 Mon Sep 17 00:00:00 2001
From: Mike Rapoport <rppt@linux.vnet.ibm.com>
Date: Wed, 2 Aug 2017 13:32:24 -0700
Subject: userfaultfd: non-cooperative: flush event_wqh at release time

From: Mike Rapoport <rppt@linux.vnet.ibm.com>

commit 5a18b64e3f02125be1c0ef777501ae38aafe2a24 upstream.

There may still be threads waiting on event_wqh at the time the
userfault file descriptor is closed.  Flush the events wait-queue to
prevent waiting threads from hanging.

Link: http://lkml.kernel.org/r/1501398127-30419-1-git-send-email-rppt@linux.vnet.ibm.com
Fixes: 9cd75c3cd4c3d ("userfaultfd: non-cooperative: add ability to report
non-PF events from uffd descriptor")
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/userfaultfd.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -851,6 +851,9 @@ wakeup:
 	__wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range);
 	spin_unlock(&ctx->fault_pending_wqh.lock);
 
+	/* Flush pending events that may still wait on event_wqh */
+	wake_up_all(&ctx->event_wqh);
+
 	wake_up_poll(&ctx->fd_wqh, POLLHUP);
 	userfaultfd_ctx_put(ctx);
 	return 0;


Patches currently in stable-queue which might be from rppt@linux.vnet.ibm.com are

queue-4.12/userfaultfd-non-cooperative-flush-event_wqh-at-release-time.patch
queue-4.12/userfaultfd_zeropage-return-enospc-in-case-mm-has-gone.patch
queue-4.12/userfaultfd-non-cooperative-notify-about-unmap-of-destination-during-mremap.patch