mount: use growable string for options

The parse_opt() routine uses fixed size of string for mount options.
This is useless for future selinux options where is not well defined
size of selinux context name.

The patch also makes code more readable and all option-string
operations share same code.

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 60 insertions, 51 deletions

diff --git a/mount/mount.c b/mount/mount.c
index f54a90e84..c0302041b 100644
--- a/mount/mount.c
+++ b/mount/mount.c
@@ -271,13 +271,40 @@ my_free(const void *s) {
 		free((void *) s);
 }
 
+/* reallocates its first arg */
+static char *
+append_opt(char *s, const char *opt, const char *val)
+{
+	if (!opt)
+		return s;
+	if (!s) {
+		if (!val)
+		       return xstrdup(opt);		/* opt */
+
+		return xstrconcat2(opt, val);		/* opt=val */
+	}
+	if (!val)
+		return xstrconcat3(s, ",", opt);	/* s,opt */
+
+	return xstrconcat4(s, ",", opt, val);		/* s,opt=val */
+}
+
+static char *
+append_numopt(char *s, const char *opt, long num)
+{
+	char buf[32];
+
+	snprintf(buf, sizeof(buf), "%ld", num);
+	return append_opt(s, opt, buf);
+}
+
 /*
  * Look for OPT in opt_map table and return mask value.
  * If OPT isn't found, tack it onto extra_opts (which is non-NULL).
  * For the options uid= and gid= replace user or group name by its value.
  */
 static inline void
-parse_opt(const char *opt, int *mask, char *extra_opts, int len) {
+parse_opt(const char *opt, int *mask, char **extra_opts) {
 	const struct opt_map *om;
 
 	for (om = opt_map; om->opt != NULL; om++)
@@ -301,39 +328,29 @@ parse_opt(const char *opt, int *mask, char *extra_opts, int len) {
 			return;
 		}
 
-	len -= strlen(extra_opts);
-
-	if (*extra_opts && --len > 0)
-		strcat(extra_opts, ",");
-
 	/* convert nonnumeric ids to numeric */
 	if (!strncmp(opt, "uid=", 4) && !isdigit(opt[4])) {
 		struct passwd *pw = getpwnam(opt+4);
-		char uidbuf[20];
 
 		if (pw) {
-			sprintf(uidbuf, "uid=%d", pw->pw_uid);
-			if ((len -= strlen(uidbuf)) > 0)
-				strcat(extra_opts, uidbuf);
+			*extra_opts = append_numopt(*extra_opts,
+						"uid=", pw->pw_uid);
 			return;
 		}
 	}
 	if (!strncmp(opt, "gid=", 4) && !isdigit(opt[4])) {
 		struct group *gr = getgrnam(opt+4);
-		char gidbuf[20];
 
 		if (gr) {
-			sprintf(gidbuf, "gid=%d", gr->gr_gid);
-			if ((len -= strlen(gidbuf)) > 0)
-				strcat(extra_opts, gidbuf);
+			*extra_opts = append_numopt(*extra_opts,
+						"gid=", gr->gr_gid);
 			return;
 		}
 	}
 
-	if ((len -= strlen(opt)) > 0)
-		strcat(extra_opts, opt);
+	*extra_opts = append_opt(*extra_opts, opt, NULL);
 }
-  
+
 /* Take -o options list and compute 4th and 5th args to mount(2).  flags
    gets the standard options (indicated by bits) and extra_opts all the rest */
 static void
@@ -346,14 +363,10 @@ parse_opts (const char *options, int *flags, char **extra_opts) {
 	if (options != NULL) {
 		char *opts = xstrdup(options);
 		char *opt;
-		int len = strlen(opts) + 20;
-
-		*extra_opts = xmalloc(len); 
-		**extra_opts = '\0';
 
 		for (opt = strtok(opts, ","); opt; opt = strtok(NULL, ","))
 			if (!parse_string_opt(opt))
-				parse_opt(opt, flags, *extra_opts, len);
+				parse_opt(opt, flags, extra_opts);
 
 		free(opts);
 	}
@@ -375,26 +388,25 @@ fix_opts_string (int flags, const char *extra_opts, const char *user) {
 	const struct string_opt_map *m;
 	char *new_opts;
 
-	new_opts = xstrdup((flags & MS_RDONLY) ? "ro" : "rw");
+	new_opts = append_opt(NULL, (flags & MS_RDONLY) ? "ro" : "rw", NULL);
 	for (om = opt_map; om->opt != NULL; om++) {
 		if (om->skip)
 			continue;
 		if (om->inv || !om->mask || (flags & om->mask) != om->mask)
 			continue;
-		new_opts = xstrconcat3(new_opts, ",", om->opt);
+		new_opts = append_opt(new_opts, om->opt, NULL);
 		flags &= ~om->mask;
 	}
 	for (m = &string_opt_map[0]; m->tag; m++) {
 		if (!m->skip && *(m->valptr))
-			new_opts = xstrconcat4(new_opts, ",",
-					       m->tag, *(m->valptr));
-	}
-	if (extra_opts && *extra_opts) {
-		new_opts = xstrconcat3(new_opts, ",", extra_opts);
-	}
-	if (user) {
-		new_opts = xstrconcat3(new_opts, ",user=", user);
+			new_opts = append_opt(new_opts, m->tag, *(m->valptr));
 	}
+	if (extra_opts && *extra_opts)
+		new_opts = append_opt(new_opts, extra_opts, NULL);
+
+	if (user)
+		new_opts = append_opt(new_opts, "user=", user);
+
 	return new_opts;
 }
 
@@ -1130,8 +1142,7 @@ retry_nfs:
 	     types = types0;
 	 }
          if (opts) {
-	     char *opts2 = xrealloc(xstrdup(opts), strlen(opts)+4);
-             strcat(opts2, ",ro");
+	     char *opts2 = append_opt(xstrdup(opts), "ro", NULL);
 	     my_free(opts1);
 	     opts = opts1 = opts2;
          } else
@@ -1185,11 +1196,14 @@ subst_string(const char *s, const char *sub, int sublen, const char *repl) {
 	return n;
 }
 
-static const char *
+static char *
 usersubst(const char *opts) {
 	char *s, *w;
 	char id[40];
 
+	if (!opts)
+		return NULL;
+
 	s = "uid=useruid";
 	if (opts && (w = strstr(opts, s)) != NULL) {
 		sprintf(id, "uid=%d", getuid());
@@ -1200,7 +1214,7 @@ usersubst(const char *opts) {
 		sprintf(id, "gid=%d", getgid());
 		opts = subst_string(opts, w, strlen(s), id);
 	}
-	return opts;
+	return xstrdup(opts);
 }
 
 static int
@@ -1215,18 +1229,16 @@ is_existing_file (const char *s) {
  */
 static int
 mount_one (const char *spec, const char *node, const char *types,
-	   const char *opts, char *cmdlineopts, int freq, int pass) {
+	   const char *fstabopts, char *cmdlineopts, int freq, int pass) {
 	int status, status2;
 	const char *nspec;
+	char *opts;
 
 	/* Substitute values in opts, if required */
-	opts = usersubst(opts);
+	opts = usersubst(fstabopts);
 
 	/* Merge the fstab and command line options.  */
-	if (opts == NULL)
-		opts = cmdlineopts;
-	else if (cmdlineopts != NULL)
-		opts = xstrconcat3(opts, ",", cmdlineopts);
+	opts = append_opt(opts, cmdlineopts, NULL);
 
 	/* Handle possible LABEL= and UUID= forms of spec */
 	nspec = mount_get_devname_for_mounting(spec);
@@ -1267,11 +1279,14 @@ mount_one (const char *spec, const char *node, const char *types,
 	spec = xstrdup(spec);		/* arguments will be destroyed */
 	node = xstrdup(node);		/* by set_proc_name()          */
 	types = xstrdup(types);
-	opts = xstrdup(opts);
 	set_proc_name (spec);		/* make a nice "ps" listing */
 	status2 = try_mount_one (spec, node, types, opts, freq, pass, 1, 0);
 	if (verbose && status2)
 		printf (_("mount: giving up \"%s\"\n"), spec);
+
+	my_free(opts);
+	my_free(node);
+	my_free(types);
 	exit (0);			/* child stops here */
 }
 
@@ -1602,16 +1617,10 @@ main(int argc, char *argv[]) {
 			++nomtab;
 			break;
 		case 'o':		/* specify mount options */
-			if (options)
-				options = xstrconcat3(options, ",", optarg);
-			else
-				options = xstrdup(optarg);
+			options = append_opt(options, optarg, NULL);
 			break;
 		case 'O':		/* with -t: mount only if (not) opt */
-			if (test_opts)
-				test_opts = xstrconcat3(test_opts, ",", optarg);
-			else
-				test_opts = xstrdup(optarg);
+			test_opts = append_opt(test_opts, optarg, NULL);
 			break;
 		case 'p':		/* fd on which to read passwd */
 			set_pfd(optarg);