CIFS: Send RFC1001 length in a separate iov

In order to simplify further encryption support we need to separate
RFC1001 length and SMB2 header when sending a request. Put the length
field in iov[0] and the rest of the packet into following iovs.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>

1 files changed, 22 insertions, 16 deletions

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index 66bd7fa9b7a6..d8af15f19dd8 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -75,24 +75,20 @@ int __cifs_calc_signature(struct smb_rqst *rqst,
 	struct kvec *iov = rqst->rq_iov;
 	int n_vec = rqst->rq_nvec;
 
-	for (i = 0; i < n_vec; i++) {
+	if (n_vec < 2 || iov[0].iov_len != 4)
+		return -EIO;
+
+	for (i = 1; i < n_vec; i++) {
 		if (iov[i].iov_len == 0)
 			continue;
 		if (iov[i].iov_base == NULL) {
 			cifs_dbg(VFS, "null iovec entry\n");
 			return -EIO;
 		}
-		/* The first entry includes a length field (which does not get
-		   signed that occupies the first 4 bytes before the header */
-		if (i == 0) {
-			if (iov[0].iov_len <= 8) /* cmd field at offset 9 */
-				break; /* nothing to sign or corrupt header */
-			rc = crypto_shash_update(shash,
-				iov[i].iov_base + 4, iov[i].iov_len - 4);
-		} else {
-			rc = crypto_shash_update(shash,
-				iov[i].iov_base, iov[i].iov_len);
-		}
+		if (i == 1 && iov[1].iov_len <= 4)
+			break; /* nothing to sign or corrupt header */
+		rc = crypto_shash_update(shash,
+					 iov[i].iov_base, iov[i].iov_len);
 		if (rc) {
 			cifs_dbg(VFS, "%s: Could not update with payload\n",
 				 __func__);
@@ -168,6 +164,10 @@ int cifs_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server,
 	char smb_signature[20];
 	struct smb_hdr *cifs_pdu = (struct smb_hdr *)rqst->rq_iov[0].iov_base;
 
+	if (rqst->rq_iov[0].iov_len != 4 ||
+	    rqst->rq_iov[0].iov_base + 4 != rqst->rq_iov[1].iov_base)
+		return -EIO;
+
 	if ((cifs_pdu == NULL) || (server == NULL))
 		return -EINVAL;
 
@@ -209,12 +209,14 @@ int cifs_sign_smbv(struct kvec *iov, int n_vec, struct TCP_Server_Info *server,
 int cifs_sign_smb(struct smb_hdr *cifs_pdu, struct TCP_Server_Info *server,
 		  __u32 *pexpected_response_sequence_number)
 {
-	struct kvec iov;
+	struct kvec iov[2];
 
-	iov.iov_base = cifs_pdu;
-	iov.iov_len = be32_to_cpu(cifs_pdu->smb_buf_length) + 4;
+	iov[0].iov_base = cifs_pdu;
+	iov[0].iov_len = 4;
+	iov[1].iov_base = (char *)cifs_pdu + 4;
+	iov[1].iov_len = be32_to_cpu(cifs_pdu->smb_buf_length);
 
-	return cifs_sign_smbv(&iov, 1, server,
+	return cifs_sign_smbv(iov, 2, server,
 			      pexpected_response_sequence_number);
 }
 
@@ -227,6 +229,10 @@ int cifs_verify_signature(struct smb_rqst *rqst,
 	char what_we_think_sig_should_be[20];
 	struct smb_hdr *cifs_pdu = (struct smb_hdr *)rqst->rq_iov[0].iov_base;
 
+	if (rqst->rq_iov[0].iov_len != 4 ||
+	    rqst->rq_iov[0].iov_base + 4 != rqst->rq_iov[1].iov_base)
+		return -EIO;
+
 	if (cifs_pdu == NULL || server == NULL)
 		return -EINVAL;