fix problem with inode revalidation and cache page invalidation

fs/cifs/AUTHORS

@@ -26,5 +26,6 @@ Test case and Bug Report contributors
 -------------------------------------
 Thanks to those in the community who have submitted detailed bug reports
 and debug of problems they have found:  Jochen Dolze, David Blaine,
-Rene Scharfe, Martin Josefsson, Alexander Wild and others. 
+Rene Scharfe, Martin Josefsson, Alexander Wild, Anthony Liguori,
+Urban Widmark, Massimiliano Ferrero, Howard Owen and others. 
 

fs/cifs/README

@@ -63,7 +63,19 @@ domain to the proper network user.  The mount.cifs mount helper can be
 trivially built from Samba 3.0 or later source e.g. by executing:
 
 	gcc samba/source/client/mount.cifs.c -o mount.cifs
-	
+
+Note that when the mount.cifs utility is run suid (allowing user mounts), 
+in order to reduce risks, the "nosuid" mount flag is passed in on mount to
+disallow execution of an suid program mounted on the remote target.
+When mount is executed as root, nosuid is not passed in by default,
+and execution of suid programs on the remote target would be enabled
+by default. This can be changed, as with nfs and other filesystems, 
+by simply specifying "nosuid" among the mount options. For user mounts 
+though to be able to pass the suid flag to mount requires rebuilding 
+mount.cifs with the following flag: 
+ 
+        gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
+
 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
 later source tree in docs/manpages/mount.cifs.8 
 
@@ -173,6 +185,15 @@ A partial list of the supported mount options follows:
 		or password or domain. This option is less important
 		when the cifs mount helper cifs.mount (version 1.1 or later)
 		is used.
+  nosuid        Do not allow remote executables with the suid bit 
+		program to be executed.  This is only meaningful for mounts
+		to servers such as Samba which support the CIFS Unix Extensions.
+		If you do not trust the servers in your network (your mount
+		targets) it is recommended that you specify this option for
+		greater security.
+  suid          Allow remote files on this mountpoint with suid enabled to 
+		be executed (default for mounts when executed as root,
+		nosuid is default for user mounts).
 
 Misc /proc/fs/cifs Flags and Debug Info
 =======================================

fs/cifs/connect.c

@@ -244,6 +244,8 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
 		}
 
 		pdu_length = 4 + ntohl(smb_buffer->smb_buf_length);
+		/* Ony read pdu_length after below checks for too short (due
+		   to e.g. int overflow) and too long ie beyond end of buf */
 		cFYI(1, ("Peek length rcvd: %d with smb length: %d", length, pdu_length));
 
 		temp = (char *) smb_buffer;
@@ -264,8 +266,8 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
 
 			} else if (temp[0] != (char) 0) {
 				cERROR(1,
-				       ("Unknown RFC 1001 frame received not 0x00 nor 0x85"));
-				cifs_dump_mem(" Received Data is: ", temp, length);
+				       ("Unknown RFC 1001 frame not 0x00 nor 0x85"));
+				cifs_dump_mem(" Received Data: ", temp, length);
 				cifs_reconnect(server);
 				csocket = server->ssocket;
 				continue;
@@ -293,8 +295,9 @@ cifs_demultiplex_thread(struct TCP_Server_Info *server)
 					length = 0;
 					iov.iov_base = smb_buffer;
 					iov.iov_len = pdu_length;
-					for (total_read = 0; total_read < pdu_length; total_read += length) {	
-             /* Should improve check for buffer overflow with bad pdu_length */
+					for (total_read = 0; 
+					     total_read < pdu_length;
+					     total_read += length) {	
 						length = sock_recvmsg(csocket, &smb_msg, 
 							pdu_length - total_read, 0);
 						if (length == 0) {

fs/cifs/file.c

@@ -375,7 +375,6 @@ cifs_close(struct inode *inode, struct file *file)
 		info on this inode, much less write behind and read ahead */
 		CIFS_I(inode)->clientCanCacheRead = FALSE;
 		CIFS_I(inode)->clientCanCacheAll  = FALSE;
-		invalidate_remote_inode(inode);
 	}
 	if((rc ==0) && CIFS_I(inode)->write_behind_rc)
 		rc = CIFS_I(inode)->write_behind_rc;

fs/cifs/inode.c

@@ -560,6 +560,20 @@ cifs_revalidate(struct dentry *direntry)
 	char *full_path;
 	struct cifs_sb_info *cifs_sb;
 	struct cifsInodeInfo *cifsInode;
+	loff_t local_size;
+        struct timespec local_mtime;	
+
+	if(direntry->d_inode == NULL)
+		return -ENOENT;
+
+	cifsInode = CIFS_I(direntry->d_inode);
+
+	if(cifsInode == NULL)
+		return -ENOENT;
+
+	/* no sense revalidating inode info on file that only we can write */
+	if(CIFS_I(direntry->d_inode)->clientCanCacheRead)
+		return rc;
 
 	xid = GetXid();
 
@@ -572,10 +586,6 @@ cifs_revalidate(struct dentry *direntry)
 	      direntry->d_inode->i_count.counter, direntry,
 	      direntry->d_time, jiffies));
 
-
-	cifsInode = CIFS_I(direntry->d_inode);
-	/* BB add check - do not need to revalidate oplocked files */
-
 	if (time_before(jiffies, cifsInode->time + HZ) && lookupCacheEnabled) {
 	    if((S_ISREG(direntry->d_inode->i_mode) == 0) || 
 			(direntry->d_inode->i_nlink == 1)) {  
@@ -587,7 +597,13 @@ cifs_revalidate(struct dentry *direntry)
 			cFYI(1,("Have to revalidate file due to hardlinks"));
 		}            
 	}
+	
+	/* save mtime and size */
+	local_mtime = direntry->d_inode->i_mtime;
+	local_size  = direntry->d_inode->i_size;
 
+	/* BB we need to write out dirty pages here if any before getting possibly 
+		stale time from server */
 	if (cifs_sb->tcon->ses->capabilities & CAP_UNIX) {
 		rc = cifs_get_inode_info_unix(&direntry->d_inode, full_path,
 					 direntry->d_sb);
@@ -607,8 +623,18 @@ cifs_revalidate(struct dentry *direntry)
 	}
 	/* should we remap certain errors, access denied?, to zero */
 
-	/* BB if not oplocked, invalidate inode pages if mtime has changed */
+	/* if not oplocked, we invalidate inode pages if mtime 
+	   or file size has changed on server */
 
+	if(timespec_equal(&local_mtime,&direntry->d_inode->i_mtime) && 
+		(local_size == direntry->d_inode->i_size)) {
+		cFYI(1,("inode unchanged on server"));
+	} else {
+		/* file has changed on server */
+		cFYI(1,("Server copy changed, invalidating remote inode "));
+		invalidate_remote_inode(direntry->d_inode);
+	}
+	
 	if (full_path)
 		kfree(full_path);
 	FreeXid(xid);

fs/cifs/misc.c

@@ -318,8 +318,8 @@ checkSMB(struct smb_hdr *smb, __u16 mid, int length)
 	     ("Entering checkSMB with Length: %x, smb_buf_length: %x ",
 	      length, ntohl(smb->smb_buf_length)));
 	if (((unsigned int)length < 2 + sizeof (struct smb_hdr))
-	    || (4 + ntohl(smb->smb_buf_length) >
-		CIFS_MAX_MSGSIZE + MAX_CIFS_HDR_SIZE)) {
+	    || (ntohl(smb->smb_buf_length) >
+		CIFS_MAX_MSGSIZE + MAX_CIFS_HDR_SIZE - 4)) {
 		if ((unsigned int)length < 2 + sizeof (struct smb_hdr)) {
 			cERROR(1, ("Length less than 2 + sizeof smb_hdr "));
 			if (((unsigned int)length >= sizeof (struct smb_hdr) - 1)
@@ -327,8 +327,8 @@ checkSMB(struct smb_hdr *smb, __u16 mid, int length)
 				return 0;	/* some error cases do not return wct and bcc */
 
 		}
-		if (4 + ntohl(smb->smb_buf_length) >
-		    CIFS_MAX_MSGSIZE + MAX_CIFS_HDR_SIZE)
+		if (ntohl(smb->smb_buf_length) >
+		    CIFS_MAX_MSGSIZE + MAX_CIFS_HDR_SIZE - 4)
 			cERROR(1,
 			       ("smb_buf_length greater than CIFS_MAX_MSGSIZE ... "));
 		cERROR(1,