selinux: rewrite selinux_sb_eat_lsm_opts()

make it use selinux_add_opt() and avoid separate copies - gather
non-LSM options by memmove() in place
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

security/selinux/hooks.c

@@ -2606,109 +2606,71 @@ static void selinux_sb_free_security(struct super_block *sb)
 	superblock_free_security(sb);
 }
 
-static inline int match_prefix(char *prefix, int plen, char *option, int olen)
+static inline int opt_len(const char *s)
 {
-	if (plen > olen)
-		return 0;
+	bool open_quote = false;
+	int len;
+	char c;
 
-	return !memcmp(prefix, option, plen);
+	for (len = 0; (c = s[len]) != '\0'; len++) {
+		if (c == '"')
+			open_quote = !open_quote;
+		if (c == ',' && !open_quote)
+			break;
+	}
+	return len;
 }
 
-static inline int selinux_option(char *option, int len)
+static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
 {
-	return (match_prefix(CONTEXT_STR, sizeof(CONTEXT_STR)-1, option, len) ||
-		match_prefix(FSCONTEXT_STR, sizeof(FSCONTEXT_STR)-1, option, len) ||
-		match_prefix(DEFCONTEXT_STR, sizeof(DEFCONTEXT_STR)-1, option, len) ||
-		match_prefix(ROOTCONTEXT_STR, sizeof(ROOTCONTEXT_STR)-1, option, len) ||
-		match_prefix(LABELSUPP_STR, sizeof(LABELSUPP_STR)-1, option, len));
-}
+	char *from = options;
+	char *to = options;
+	bool first = true;
 
-static inline void take_option(char **to, char *from, int *first, int len)
-{
-	if (!*first) {
-		**to = ',';
-		*to += 1;
-	} else
-		*first = 0;
-	memcpy(*to, from, len);
-	*to += len;
-}
+	while (1) {
+		int len = opt_len(from);
+		int token, rc;
+		char *arg = NULL;
 
-static inline void take_selinux_option(char **to, char *from, int *first,
-				       int len)
-{
-	int current_size = 0;
+		token = match_opt_prefix(from, len, &arg);
 
-	if (!*first) {
-		**to = '|';
-		*to += 1;
-	} else
-		*first = 0;
+		if (token != Opt_error) {
+			char *p, *q;
 
-	while (current_size < len) {
-		if (*from != '"') {
-			**to = *from;
-			*to += 1;
+			/* strip quotes */
+			if (arg) {
+				for (p = q = arg; p < from + len; p++) {
+					char c = *p;
+					if (c != '"')
+						*q++ = c;
 				}
-		from += 1;
-		current_size += 1;
+				arg = kmemdup_nul(arg, q - arg, GFP_KERNEL);
 			}
-}
-
-static int selinux_sb_copy_data(char *orig, char *copy)
-{
-	int fnosec, fsec, rc = 0;
-	char *in_save, *in_curr, *in_end;
-	char *sec_curr, *nosec_save, *nosec;
-	int open_quote = 0;
-
-	in_curr = orig;
-	sec_curr = copy;
-
-	nosec = (char *)get_zeroed_page(GFP_KERNEL);
-	if (!nosec) {
-		rc = -ENOMEM;
-		goto out;
-	}
-
-	nosec_save = nosec;
-	fnosec = fsec = 1;
-	in_save = in_end = orig;
-
-	do {
-		if (*in_end == '"')
-			open_quote = !open_quote;
-		if ((*in_end == ',' && open_quote == 0) ||
-				*in_end == '\0') {
-			int len = in_end - in_curr;
-
-			if (selinux_option(in_curr, len))
-				take_selinux_option(&sec_curr, in_curr, &fsec, len);
-			else
-				take_option(&nosec, in_curr, &fnosec, len);
-
-			in_curr = in_end + 1;
+			rc = selinux_add_opt(token, arg, mnt_opts);
+			if (unlikely(rc)) {
+				kfree(arg);
+				if (*mnt_opts) {
+					selinux_free_mnt_opts(*mnt_opts);
+					*mnt_opts = NULL;
 				}
-	} while (*in_end++);
-
-	strcpy(in_save, nosec_save);
-	free_page((unsigned long)nosec_save);
-out:
 				return rc;
-}
-
-static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
-{
-	char *s = (char *)get_zeroed_page(GFP_KERNEL);
-	int err;
-
-	if (!s)
-		return -ENOMEM;
-	err = selinux_sb_copy_data(options, s);
-	if (!err)
-		err = selinux_parse_opts_str(s, mnt_opts);
-	free_page((unsigned long)s);
-	return err;
+			}
+		} else {
+			if (!first) {	// copy with preceding comma
+				from--;
+				len++;
+			}
+			if (to != from)
+				memmove(to, from, len);
+			to += len;
+			first = false;
+		}
+		if (!from[len])
+			break;
+		from += len + 1;
+	}
+	*to = '\0';
+	return 0;
 }
 
 static int selinux_sb_remount(struct super_block *sb, void *mnt_opts)