[CIFS] Fix large (ie over 64K for MaxCIFSBufSize) buffer case for wrapping

bcc on read response and for wrapping sessionsetup maxbufsize field

Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/CHANGES

@@ -2,7 +2,11 @@ Version 1.41
 ------------
 Fix NTLMv2 security (can be enabled in /proc/fs/cifs) so customers can
 configure stronger authentication.  Fix sfu symlinks so they can
-be followed (not just recognized).
+be followed (not just recognized).  Fix wraparound of bcc on
+read responses when buffer size over 64K and also fix wrap of
+max smb buffer size when CIFSMaxBufSize over 64K.  Fix oops in
+cifs_user_read and cifs_readpages (when EAGAIN on send of smb
+on socket is returned over and over)
 
 Version 1.40
 ------------

fs/cifs/connect.c

@@ -564,7 +564,7 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
 	
 
 		dump_smb(smb_buffer, length);
-		if (checkSMB (smb_buffer, smb_buffer->Mid, total_read+4)) {
+		if (checkSMB(smb_buffer, smb_buffer->Mid, total_read+4)) {
 			cifs_dump_mem("Bad SMB: ", smb_buffer, 48);
 			continue;
 		}
@@ -2278,6 +2278,8 @@ CIFSSpnegoSessSetup(unsigned int xid, struct cifsSesInfo *ses,
 	smb_buffer->Mid = GetNextMid(ses->server);
 	pSMB->req.hdr.Flags2 |= SMBFLG2_EXT_SEC;
 	pSMB->req.AndXCommand = 0xFF;
+	if(ses->server->maxBuf > 64*1024)
+		ses->server->maxBuf = (64*1023);
 	pSMB->req.MaxBufferSize = cpu_to_le16(ses->server->maxBuf);
 	pSMB->req.MaxMpxCount = cpu_to_le16(ses->server->maxReq);
 

fs/cifs/misc.c

@@ -421,9 +421,7 @@ checkSMB(struct smb_hdr *smb, __u16 mid, int length)
 {
 	__u32 len = smb->smb_buf_length;
 	__u32 clc_len;  /* calculated length */
-	cFYI(0,
-	     ("Entering checkSMB with Length: %x, smb_buf_length: %x",
-	      length, len));
+	cFYI(0, ("checkSMB Length: 0x%x, smb_buf_length: 0x%x", length, len));
 	if (((unsigned int)length < 2 + sizeof (struct smb_hdr)) ||
 	    (len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4)) {
 		if ((unsigned int)length < 2 + sizeof (struct smb_hdr)) {
@@ -435,22 +433,29 @@ checkSMB(struct smb_hdr *smb, __u16 mid, int length)
 			} else {
 				cERROR(1, ("Length less than smb header size"));
 			}
-
 		}
 		if (len > CIFSMaxBufSize + MAX_CIFS_HDR_SIZE - 4)
-			cERROR(1,
-			       ("smb_buf_length greater than MaxBufSize"));
-		cERROR(1,
-		       ("bad smb detected. Illegal length. mid=%d",
-			smb->Mid));
+			cERROR(1, ("smb length greater than MaxBufSize, mid=%d",
+				   smb->Mid));
 		return 1;
 	}
 
 	if (checkSMBhdr(smb, mid))
 		return 1;
 	clc_len = smbCalcSize_LE(smb);
-	if ((4 + len != clc_len)
-	    || (4 + len != (unsigned int)length)) {
+
+	if(4 + len != (unsigned int)length) {
+		cERROR(1, ("Length read does not match RFC1001 length %d",len));
+		return 1;
+	}
+
+	if (4 + len != clc_len) {
+		/* check if bcc wrapped around for large read responses */
+		if((len > 64 * 1024) && (len > clc_len)) {
+			/* check if lengths match mod 64K */
+			if(((4 + len) & 0xFFFF) == (clc_len & 0xFFFF))
+				return 0; /* bcc wrapped */			
+		}
 		cERROR(1, ("Calculated size 0x%x vs actual length 0x%x",
 				clc_len, 4 + len));
 		cERROR(1, ("bad smb size detected for Mid=%d", smb->Mid));