[3.19.y-ckt stable] Patch "nfs4: start callback_ident at idr 1" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    nfs4: start callback_ident at idr 1

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From aea269033941d94e68f17ab2a4cc1b44e66581f4 Mon Sep 17 00:00:00 2001
From: Benjamin Coddington <bcodding at redhat.com>
Date: Fri, 20 Nov 2015 09:56:20 -0500
Subject: nfs4: start callback_ident at idr 1

commit c68a027c05709330fe5b2f50c50d5fa02124b5d8 upstream.

If clp->cl_cb_ident is zero, then nfs_cb_idr_remove_locked() skips removing
it when the nfs_client is freed.  A decoding or server bug can then find
and try to put that first nfs_client which would lead to a crash.

Signed-off-by: Benjamin Coddington <bcodding at redhat.com>
Fixes: d6870312659d ("nfs4client: convert to idr_alloc()")
Signed-off-by: Trond Myklebust <trond.myklebust at primarydata.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/nfs/nfs4client.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 706ad10..ca7527d 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -33,7 +33,7 @@ static int nfs_get_cb_ident_idr(struct nfs_client *clp, int minorversion)
 		return ret;
 	idr_preload(GFP_KERNEL);
 	spin_lock(&nn->nfs_client_lock);
-	ret = idr_alloc(&nn->cb_ident_idr, clp, 0, 0, GFP_NOWAIT);
+	ret = idr_alloc(&nn->cb_ident_idr, clp, 1, 0, GFP_NOWAIT);
 	if (ret >= 0)
 		clp->cl_cb_ident = ret;
 	spin_unlock(&nn->nfs_client_lock);
--
1.9.1