Patch "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter" has been added to the 4.9-stable tree

Patch "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter" has been added to the 4.9-stable tree

[gregkh]

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

    NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter

to the 4.9-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:
     nfsv4.1-fix-a-race-where-cb_notify_lock-fails-to-wake-a-waiter.patch
and it can be found in the queue-4.9 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 b7dbcc0e433f0f61acb89ed9861ec996be4f2b38 Mon Sep 17 00:00:00 2001
From: Benjamin Coddington <bcodding@redhat.com>
Date: Fri, 28 Jul 2017 12:33:54 -0400
Subject: NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter

From: Benjamin Coddington <bcodding@redhat.com>

commit b7dbcc0e433f0f61acb89ed9861ec996be4f2b38 upstream.

nfs4_retry_setlk() sets the task's state to TASK_INTERRUPTIBLE within the
same region protected by the wait_queue's lock after checking for a
notification from CB_NOTIFY_LOCK callback.  However, after releasing that
lock, a wakeup for that task may race in before the call to
freezable_schedule_timeout_interruptible() and set TASK_WAKING, then
freezable_schedule_timeout_interruptible() will set the state back to
TASK_INTERRUPTIBLE before the task will sleep.  The result is that the task
will sleep for the entire duration of the timeout.

Since we've already set TASK_INTERRUPTIBLE in the locked section, just use
freezable_schedule_timout() instead.

Fixes: a1d617d8f134 ("nfs: allow blocking locks to be awoken by lock callbacks")
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/nfs/nfs4proc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -6419,7 +6419,7 @@ nfs4_retry_setlk(struct nfs4_state *stat
 		set_current_state(TASK_INTERRUPTIBLE);
 		spin_unlock_irqrestore(&q->lock, flags);
 
-		freezable_schedule_timeout_interruptible(NFS4_LOCK_MAXTIMEOUT);
+		freezable_schedule_timeout(NFS4_LOCK_MAXTIMEOUT);
 	}
 
 	finish_wait(q, &wait);


Patches currently in stable-queue which might be from bcodding@redhat.com are

queue-4.9/nfsv4.1-fix-a-race-where-cb_notify_lock-fails-to-wake-a-waiter.patch