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>

1 files changed, 24 insertions, 7 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index ee70075c5fb1..5308bc6e1248 100644
--- 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;