cifs: add a third receive phase to cifs_demultiplex_thread

Have the demultiplex thread receive just enough to get to the MID, and
then find it before receiving the rest. Later, we'll use this to swap
in a preallocated receive buffer for some calls.

Reviewed-and-Tested-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index ee70075..5308bc6 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -746,11 +746,25 @@ cifs_demultiplex_thread(void *p)
                if (!is_smb_response(server, buf[0]))
                        continue;
 
-               /* check the length */
-               if ((pdu_length > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4) ||
-                   (pdu_length < sizeof(struct smb_hdr) - 1 - 4)) {
-                       cERROR(1, "Invalid size SMB length %d pdu_length %d",
-                              4, pdu_length + 4);
+               /* make sure we have enough to get to the MID */
+               if (pdu_length < sizeof(struct smb_hdr) - 1 - 4) {
+                       cERROR(1, "SMB response too short (%u bytes)",
+                               pdu_length);
+                       cifs_reconnect(server);
+                       wake_up(&server->response_q);
+                       continue;
+               }
+
+               /* read down to the MID */
+               length = read_from_socket(server, buf + 4,
+                                         sizeof(struct smb_hdr) - 1 - 4);
+               if (length < 0)
+                       continue;
+               total_read += length;
+
+               if (pdu_length > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4) {
+                       cERROR(1, "SMB response too long (%u bytes)",
+                               pdu_length);
                        cifs_reconnect(server);
                        wake_up(&server->response_q);
                        continue;
@@ -759,12 +773,15 @@ cifs_demultiplex_thread(void *p)
                /* else length ok */
                if (pdu_length > MAX_CIFS_SMALL_BUFFER_SIZE - 4) {
                        isLargeBuf = true;
-                       memcpy(bigbuf, smallbuf, 4);
+                       memcpy(bigbuf, smallbuf, total_read);
                        smb_buffer = (struct smb_hdr *)bigbuf;
                        buf = bigbuf;
                }
 
-               length = read_from_socket(server, buf + 4, pdu_length);
+               /* now read the rest */
+               length = read_from_socket(server,
+                                 buf + sizeof(struct smb_hdr) - 1,
+                                 pdu_length - sizeof(struct smb_hdr) + 1 + 4);
                if (length < 0)
                        continue;
                total_read += length;