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;