[PATCH][CIFS] Workaround MacOS server problem with SMB2.1 write response

Steve French smfrench at gmail.com
Tue Aug 12 08:19:42 MDT 2014


Writes fail to Mac servers with SMB2.1 mounts (works with cifs though) due
to them sending an incorrect RFC1001 length. Workaround this problem.
MacOS server sends a write response with 3 bytes of pad beyond the end
of the SMB itself.  The RFC1001 length is 3 bytes more than
the sum of the SMB2.1 header length + the write reponse.

Since we have seen a few other examples where servers have
padded responses strangely (oplock break and create),
allow servers to send a padded SMB2/SMB3 response to allow
for rounding (up to 15 bytes).

Signed-off-by: Steve French <smfrench at gmail.com>
---
 fs/cifs/smb2misc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index f2e6ac2..da05beb 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -181,6 +181,12 @@ smb2_check_message(char *buf, unsigned int length)
         /* server can return one byte more */
         if (clc_len == 4 + len + 1)
             return 0;
+
+        /* MacOS server pads after SMB2.1 write response with 3 bytes */
+        /* of junk. Allow server to pad up to 15 bytes of junk at end */
+        if ((clc_len < 4 + len) && (clc_len > 4 + len - 16))
+            return 0;
+
         return 1;
     }
     return 0;

-- 
Thanks,

Steve


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