4.12-stable review patch.  If anyone has any objections, please let me know.


From: Mike Rapoport <r...@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.

Fixes: 9cd75c3cd4c3d ("userfaultfd: non-cooperative: add ability to report
non-PF events from uffd descriptor")
Signed-off-by: Mike Rapoport <r...@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
Cc: Pavel Emelyanov <xe...@virtuozzo.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@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);
+       /* Flush pending events that may still wait on event_wqh */
+       wake_up_all(&ctx->event_wqh);
        wake_up_poll(&ctx->fd_wqh, POLLHUP);
        return 0;

Reply via email to