[PATCH] CIFS: do not send invalid input buffer on QUERY_INFO requests

[Aurelien Aptel <aaptel-IBi9RG/b67k@public.gmane.org>]

query_info() doesn't use the InputBuffer field of the QUERY_INFO
request, therefore according to [MS-SMB2] it must:

a) set the InputBufferOffset to 0
b) send a zero-length InputBuffer

Doing a) is trivial but b) is a bit more tricky.

The packet is allocated according to it's StructureSize, which takes
into account an extra 1 byte buffer which we don't need
here. StructureSize fields must have constant values no matter the
actual length of the whole packet so we can't just edit that constant.

Both the NetBIOS-over-TCP message length ("rfc1002 length") L and the
iovec length L' have to be updated. Since L' is computed from L we
just update L by decrementing it by one.

Signed-off-by: Aurelien Aptel <aaptel-IBi9RG/b67k@public.gmane.org>
---
 fs/cifs/smb2pdu.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 6f0e6343c15e..b927e131f997 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -2191,9 +2191,13 @@ query_info(const unsigned int xid, struct cifs_tcon *tcon,
 	req->PersistentFileId = persistent_fid;
 	req->VolatileFileId = volatile_fid;
 	req->AdditionalInformation = cpu_to_le32(additional_info);
-	/* 4 for rfc1002 length field and 1 for Buffer */
-	req->InputBufferOffset =
-		cpu_to_le16(sizeof(struct smb2_query_info_req) - 1 - 4);
+
+	/*
+	 * We do not use the input buffer (do not send extra byte)
+	 */
+	req->InputBufferOffset = 0;
+	inc_rfc1001_len(req, -1);
+
 	req->OutputBufferLength = cpu_to_le32(output_len);
 
 	iov[0].iov_base = (char *)req;
-- 
2.12.3