From: Roberto Bergantinos Corpas <rbergant@redhat.com>
Date: Mon, 14 Oct 2019 10:59:23 +0200
Subject: [PATCH] CIFS: avoid using MID 0xFFFF
Git-commit: 03d9a9fe3f3aec508e485dd3dcfa1e99933b4bdb
References: bsc#1144333 bsc#1154355
Patch-mainline: v5.4-rc5
According to MS-CIFS specification MID 0xFFFF should not be used by the
CIFS client, but we actually do. Besides, this has proven to cause races
leading to oops between SendReceive2/cifs_demultiplex_thread. On SMB1,
MID is a 2 byte value easy to reach in CurrentMid which may conflict with
an oplock break notification request coming from server
Signed-off-by: Roberto Bergantinos Corpas <rbergant@redhat.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>
Acked-by: Paulo Alcantara <palcantara@suse.de
---
fs/cifs/smb1ops.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/fs/cifs/smb1ops.c b/fs/cifs/smb1ops.c
index b7421a096319..514810694c0f 100644
--- a/fs/cifs/smb1ops.c
+++ b/fs/cifs/smb1ops.c
@@ -171,6 +171,9 @@ cifs_get_next_mid(struct TCP_Server_Info *server)
/* we do not want to loop forever */
last_mid = cur_mid;
cur_mid++;
+ /* avoid 0xFFFF MID */
+ if (cur_mid == 0xffff)
+ cur_mid++;
/*
* This nested loop looks more expensive than it is.
--
2.23.0