selinux: kill selinux_sb_get_mnt_opts()

it's much easier to just do the right thing in ->sb_show_options(),
without bothering with allocating and populating arrays, etc.
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

security/selinux/hooks.c

@@ -591,105 +591,6 @@ static int sb_finish_set_opts(struct super_block *sb)
 	return rc;
 }
 
-/*
- * This function should allow an FS to ask what it's mount security
- * options were so it can use those later for submounts, displaying
- * mount options, or whatever.
- */
-static int selinux_get_mnt_opts(const struct super_block *sb,
-				struct security_mnt_opts *opts)
-{
-	int rc = 0, i;
-	struct superblock_security_struct *sbsec = sb->s_security;
-	char *context = NULL;
-	u32 len;
-	char tmp;
-
-	security_init_mnt_opts(opts);
-
-	if (!(sbsec->flags & SE_SBINITIALIZED))
-		return -EINVAL;
-
-	if (!selinux_state.initialized)
-		return -EINVAL;
-
-	/* make sure we always check enough bits to cover the mask */
-	BUILD_BUG_ON(SE_MNTMASK >= (1 << NUM_SEL_MNT_OPTS));
-
-	tmp = sbsec->flags & SE_MNTMASK;
-	/* count the number of mount options for this sb */
-	for (i = 0; i < NUM_SEL_MNT_OPTS; i++) {
-		if (tmp & 0x01)
-			opts->num_mnt_opts++;
-		tmp >>= 1;
-	}
-	/* Check if the Label support flag is set */
-	if (sbsec->flags & SBLABEL_MNT)
-		opts->num_mnt_opts++;
-
-	opts->mnt_opts = kcalloc(opts->num_mnt_opts, sizeof(char *), GFP_ATOMIC);
-	if (!opts->mnt_opts) {
-		rc = -ENOMEM;
-		goto out_free;
-	}
-
-	opts->mnt_opts_flags = kcalloc(opts->num_mnt_opts, sizeof(int), GFP_ATOMIC);
-	if (!opts->mnt_opts_flags) {
-		rc = -ENOMEM;
-		goto out_free;
-	}
-
-	i = 0;
-	if (sbsec->flags & FSCONTEXT_MNT) {
-		rc = security_sid_to_context(&selinux_state, sbsec->sid,
-					     &context, &len);
-		if (rc)
-			goto out_free;
-		opts->mnt_opts[i] = context;
-		opts->mnt_opts_flags[i++] = FSCONTEXT_MNT;
-	}
-	if (sbsec->flags & CONTEXT_MNT) {
-		rc = security_sid_to_context(&selinux_state,
-					     sbsec->mntpoint_sid,
-					     &context, &len);
-		if (rc)
-			goto out_free;
-		opts->mnt_opts[i] = context;
-		opts->mnt_opts_flags[i++] = CONTEXT_MNT;
-	}
-	if (sbsec->flags & DEFCONTEXT_MNT) {
-		rc = security_sid_to_context(&selinux_state, sbsec->def_sid,
-					     &context, &len);
-		if (rc)
-			goto out_free;
-		opts->mnt_opts[i] = context;
-		opts->mnt_opts_flags[i++] = DEFCONTEXT_MNT;
-	}
-	if (sbsec->flags & ROOTCONTEXT_MNT) {
-		struct dentry *root = sbsec->sb->s_root;
-		struct inode_security_struct *isec = backing_inode_security(root);
-
-		rc = security_sid_to_context(&selinux_state, isec->sid,
-					     &context, &len);
-		if (rc)
-			goto out_free;
-		opts->mnt_opts[i] = context;
-		opts->mnt_opts_flags[i++] = ROOTCONTEXT_MNT;
-	}
-	if (sbsec->flags & SBLABEL_MNT) {
-		opts->mnt_opts[i] = NULL;
-		opts->mnt_opts_flags[i++] = SBLABEL_MNT;
-	}
-
-	BUG_ON(i != opts->num_mnt_opts);
-
-	return 0;
-
-out_free:
-	security_free_mnt_opts(opts);
-	return rc;
-}
-
 static int bad_option(struct superblock_security_struct *sbsec, char flag,
 		      u32 old_sid, u32 new_sid)
 {
@@ -1201,70 +1102,73 @@ static int selinux_parse_opts_str(char *options,
 	return rc;
 }
 
-static void selinux_write_opts(struct seq_file *m,
-			       struct security_mnt_opts *opts)
+static int show_sid(struct seq_file *m, u32 sid)
 {
-	int i;
-	char *prefix;
-
-	for (i = 0; i < opts->num_mnt_opts; i++) {
-		char *has_comma;
+	char *context = NULL;
+	u32 len;
+	int rc;
 
-		if (opts->mnt_opts[i])
-			has_comma = strchr(opts->mnt_opts[i], ',');
-		else
-			has_comma = NULL;
+	rc = security_sid_to_context(&selinux_state, sid,
+					     &context, &len);
+	if (!rc) {
+		bool has_comma = context && strchr(context, ',');
 
-		switch (opts->mnt_opts_flags[i]) {
-		case CONTEXT_MNT:
-			prefix = CONTEXT_STR;
-			break;
-		case FSCONTEXT_MNT:
-			prefix = FSCONTEXT_STR;
-			break;
-		case ROOTCONTEXT_MNT:
-			prefix = ROOTCONTEXT_STR;
-			break;
-		case DEFCONTEXT_MNT:
-			prefix = DEFCONTEXT_STR;
-			break;
-		case SBLABEL_MNT:
-			seq_putc(m, ',');
-			seq_puts(m, LABELSUPP_STR);
-			continue;
-		default:
-			BUG();
-			return;
-		};
-		/* we need a comma before each option */
-		seq_putc(m, ',');
-		seq_puts(m, prefix);
 		if (has_comma)
 			seq_putc(m, '\"');
-		seq_escape(m, opts->mnt_opts[i], "\"\n\\");
+		seq_escape(m, context, "\"\n\\");
 		if (has_comma)
 			seq_putc(m, '\"');
 	}
+	kfree(context);
+	return rc;
 }
 
 static int selinux_sb_show_options(struct seq_file *m, struct super_block *sb)
 {
-	struct security_mnt_opts opts;
+	struct superblock_security_struct *sbsec = sb->s_security;
 	int rc;
 
-	rc = selinux_get_mnt_opts(sb, &opts);
-	if (rc) {
-		/* before policy load we may get EINVAL, don't show anything */
-		if (rc == -EINVAL)
-			rc = 0;
-		return rc;
-	}
-
-	selinux_write_opts(m, &opts);
+	if (!(sbsec->flags & SE_SBINITIALIZED))
+		return 0;
 
-	security_free_mnt_opts(&opts);
+	if (!selinux_state.initialized)
+		return 0;
 
+	if (sbsec->flags & FSCONTEXT_MNT) {
+		seq_putc(m, ',');
+		seq_puts(m, FSCONTEXT_STR);
+		rc = show_sid(m, sbsec->sid);
+		if (rc)
 			return rc;
+	}
+	if (sbsec->flags & CONTEXT_MNT) {
+		seq_putc(m, ',');
+		seq_puts(m, CONTEXT_STR);
+		rc = show_sid(m, sbsec->mntpoint_sid);
+		if (rc)
+			return rc;
+	}
+	if (sbsec->flags & DEFCONTEXT_MNT) {
+		seq_putc(m, ',');
+		seq_puts(m, DEFCONTEXT_STR);
+		rc = show_sid(m, sbsec->def_sid);
+		if (rc)
+			return rc;
+	}
+	if (sbsec->flags & ROOTCONTEXT_MNT) {
+		struct dentry *root = sbsec->sb->s_root;
+		struct inode_security_struct *isec = backing_inode_security(root);
+		seq_putc(m, ',');
+		seq_puts(m, ROOTCONTEXT_STR);
+		rc = show_sid(m, isec->sid);
+		if (rc)
+			return rc;
+	}
+	if (sbsec->flags & SBLABEL_MNT) {
+		seq_putc(m, ',');
+		seq_puts(m, LABELSUPP_STR);
+	}
+	return 0;
 }
 
 static inline u16 inode_mode_to_security_class(umode_t mode)