cifs: fix up handling of prefixpath= option

Currently the code takes care to ensure that the prefixpath has a
leading '/' delimiter. What if someone passes us a prefixpath with a
leading '\\' instead? The code doesn't properly handle that currently
AFAICS.

Let's just change the code to skip over any leading delimiter character
when copying the prepath. Then, fix up the users of the prepath option
to prefix it with the correct delimiter when they use it.

Also, there's no need to limit the length of the prefixpath to 1k. If
the server can handle it, why bother forbidding it?

Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/connect.c

@@ -1612,31 +1612,14 @@ cifs_parse_mount_options(const char *mountdata, const char *devname,
 			}
 			break;
 		case Opt_prefixpath:
-			string = match_strdup(args);
-			if (string == NULL)
+			/* skip over any leading delimiter */
+			if (*args[0].from == '/' || *args[0].from == '\\')
+				args[0].from++;
+
+			kfree(vol->prepath);
+			vol->prepath = match_strdup(args);
+			if (vol->prepath == NULL)
 				goto out_nomem;
-
-			temp_len = strnlen(string, 1024);
-			if (string[0] != '/')
-				temp_len++; /* missing leading slash */
-			if (temp_len > 1024) {
-				printk(KERN_WARNING "CIFS: prefix too long\n");
-				goto cifs_parse_mount_err;
-			}
-
-			vol->prepath = kmalloc(temp_len+1, GFP_KERNEL);
-			if (vol->prepath == NULL) {
-				printk(KERN_WARNING "CIFS: no memory "
-						    "for path prefix\n");
-				goto cifs_parse_mount_err;
-			}
-
-			if (string[0] != '/') {
-				vol->prepath[0] = '/';
-				strcpy(vol->prepath+1, string);
-			} else
-				strcpy(vol->prepath, string);
-
 			break;
 		case Opt_iocharset:
 			string = match_strdup(args);
@@ -3236,7 +3219,7 @@ build_unc_path_to_root(const struct smb_vol *vol,
 		const struct cifs_sb_info *cifs_sb)
 {
 	char *full_path, *pos;
-	unsigned int pplen = vol->prepath ? strlen(vol->prepath) : 0;
+	unsigned int pplen = vol->prepath ? strlen(vol->prepath) + 1 : 0;
 	unsigned int unc_len = strnlen(vol->UNC, MAX_TREE_SIZE + 1);
 
 	full_path = kmalloc(unc_len + pplen + 1, GFP_KERNEL);
@@ -3247,6 +3230,7 @@ build_unc_path_to_root(const struct smb_vol *vol,
 	pos = full_path + unc_len;
 
 	if (pplen) {
+		*pos++ = CIFS_DIR_SEP(cifs_sb);
 		strncpy(pos, vol->prepath, pplen);
 		pos += pplen;
 	}

fs/cifs/dir.c

@@ -48,7 +48,7 @@ char *
 cifs_build_path_to_root(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
 			struct cifs_tcon *tcon)
 {
-	int pplen = vol->prepath ? strlen(vol->prepath) : 0;
+	int pplen = vol->prepath ? strlen(vol->prepath) + 1 : 0;
 	int dfsplen;
 	char *full_path = NULL;
 
@@ -69,7 +69,8 @@ cifs_build_path_to_root(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
 
 	if (dfsplen)
 		strncpy(full_path, tcon->treeName, dfsplen);
-	strncpy(full_path + dfsplen, vol->prepath, pplen);
+	full_path[dfsplen] = CIFS_DIR_SEP(cifs_sb);
+	strncpy(full_path + dfsplen + 1, vol->prepath, pplen);
 	convert_delimiter(full_path, CIFS_DIR_SEP(cifs_sb));
 	full_path[dfsplen + pplen] = 0; /* add trailing null */
 	return full_path;