LSM: hide struct security_mnt_opts from any generic code

Keep void * instead, allocate on demand (in parse_str_opts, at the
moment).  Eventually both selinux and smack will be better off
with private structures with several strings in those, rather than
this "counter and two pointers to dynamically allocated arrays"
ugliness.  This commit allows to do that at leisure, without
disrupting anything outside of given module.

Changes:
	* instead of struct security_mnt_opt use an opaque pointer
initialized to NULL.
	* security_sb_eat_lsm_opts(), security_sb_parse_opts_str() and
security_free_mnt_opts() take it as var argument (i.e. as void **);
call sites are unchanged.
	* security_sb_set_mnt_opts() and security_sb_remount() take
it by value (i.e. as void *).
	* new method: ->sb_free_mnt_opts().  Takes void *, does
whatever freeing that needs to be done.
	* ->sb_set_mnt_opts() and ->sb_remount() might get NULL as
mnt_opts argument, meaning "empty".

Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 6 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 3b04e7735b5f..e90c4616ed6a 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1472,14 +1472,13 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 	struct btrfs_device *device = NULL;
 	struct btrfs_fs_devices *fs_devices = NULL;
 	struct btrfs_fs_info *fs_info = NULL;
-	struct security_mnt_opts new_sec_opts;
+	void *new_sec_opts = NULL;
 	fmode_t mode = FMODE_READ;
 	int error = 0;
 
 	if (!(flags & SB_RDONLY))
 		mode |= FMODE_WRITE;
 
-	security_init_mnt_opts(&new_sec_opts);
 	if (data) {
 		error = security_sb_eat_lsm_opts(data, &new_sec_opts);
 		if (error)
@@ -1551,7 +1550,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 		error = btrfs_fill_super(s, fs_devices, data);
 	}
 	if (!error)
-		error = security_sb_set_mnt_opts(s, &new_sec_opts, 0, NULL);
+		error = security_sb_set_mnt_opts(s, new_sec_opts, 0, NULL);
 	security_free_mnt_opts(&new_sec_opts);
 	if (error) {
 		deactivate_locked_super(s);
@@ -1724,12 +1723,11 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 	btrfs_remount_prepare(fs_info);
 
 	if (data) {
-		struct security_mnt_opts new_sec_opts;
+		void *new_sec_opts = NULL;
 
-		security_init_mnt_opts(&new_sec_opts);
 		ret = security_sb_eat_lsm_opts(data, &new_sec_opts);
 		if (!ret)
-			ret = security_sb_remount(sb, &new_sec_opts);
+			ret = security_sb_remount(sb, new_sec_opts);
 		security_free_mnt_opts(&new_sec_opts);
 		if (ret)
 			goto restore;