linux-kernel - [PATCH 4.9 16/78] cifs: check if SMB2 PDU size has been padded and suppress the warning

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Date:   Thu, 13 Sep 2018 15:31:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ronnie Sahlberg <lsahlber@...hat.com>,
        Steve French <stfrench@...rosoft.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.9 16/78] cifs: check if SMB2 PDU size has been padded and suppress the warning

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

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

From: Ronnie Sahlberg <lsahlber@...hat.com>

[ Upstream commit e6c47dd0da1e3a484e778046fc10da0b20606a86 ]

Some SMB2/3 servers, Win2016 but possibly others too, adds padding
not only between PDUs in a compound but also to the final PDU.
This padding extends the PDU to a multiple of 8 bytes.

Check if the unexpected length looks like this might be the case
and avoid triggering the log messages for :

  "SMB2 server sent bad RFC1001 len %d not %d\n"

Signed-off-by: Ronnie Sahlberg <lsahlber@...hat.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/cifs/smb2misc.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -209,6 +209,13 @@ smb2_check_message(char *buf, unsigned i
 			return 0;
 
 		/*
+		 * Some windows servers (win2016) will pad also the final
+		 * PDU in a compound to 8 bytes.
+		 */
+		if (((clc_len + 7) & ~7) == len)
+			return 0;
+
+		/*
 		 * MacOS server pads after SMB2.1 write response with 3 bytes
 		 * of junk. Other servers match RFC1001 len to actual
 		 * SMB2/SMB3 frame length (header + smb2 response specific data)