From: Mike Rapoport <rppt@linux.vnet.ibm.com>
Date: Wed, 2 Aug 2017 20:32:24 +0000 (-0700)
Subject: userfaultfd: non-cooperative: flush event_wqh at release time
X-Git-Tag: v4.13-rc4~21^2~2
X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=commitdiff_plain;h=5a18b64e3f02125be1c0ef777501ae38aafe2a24;ds=sidebyside

userfaultfd: non-cooperative: flush event_wqh at release time

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 2d8c2d848668..06ea26b8c996 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -854,6 +854,9 @@ 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;