[PATCH 4.17 182/220] NFSv4: Revert commit 5f83d86cf531d ("NFSv4.x: Fix wraparound issues..")

[Greg Kroah-Hartman]

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

------------------

From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>

commit fc40724fc6731d90cc7fb6d62d66135f85a33dd2 upstream.

The correct behaviour for NFSv4 sequence IDs is to wrap around
to the value 0 after 0xffffffff.
See https://tools.ietf.org/html/rfc5661#section-2.10.6.1

Fixes: 5f83d86cf531d ("NFSv4.x: Fix wraparound issues when validing...")
Cc: stable@xxxxxxxxxxxxxxx # 4.6+
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/nfs/callback_proc.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -420,11 +420,8 @@ validate_seqid(const struct nfs4_slot_ta
 		return htonl(NFS4ERR_SEQ_FALSE_RETRY);
 	}
 
-	/* Wraparound */
-	if (unlikely(slot->seq_nr == 0xFFFFFFFFU)) {
-		if (args->csa_sequenceid == 1)
-			return htonl(NFS4_OK);
-	} else if (likely(args->csa_sequenceid == slot->seq_nr + 1))
+	/* Note: wraparound relies on seq_nr being of type u32 */
+	if (likely(args->csa_sequenceid == slot->seq_nr + 1))
 		return htonl(NFS4_OK);
 
 	/* Misordered request */