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, 5 insertions, 7 deletions

diff --git a/fs/super.c b/fs/super.c
index 1f75fe312597..a5511c4ba69b 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1247,12 +1247,10 @@ mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
         struct dentry *root;
         struct super_block *sb;
         int error = -ENOMEM;
-        struct security_mnt_opts opts;
-
-        security_init_mnt_opts(&opts);
+        void *sec_opts = NULL;
 
         if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
-                error = security_sb_eat_lsm_opts(data, &opts);
+                error = security_sb_eat_lsm_opts(data, &sec_opts);
                 if (error)
                         return ERR_PTR(error);
         }
@@ -1275,7 +1273,7 @@ mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
         smp_wmb();
         sb->s_flags |= SB_BORN;
 
-        error = security_sb_set_mnt_opts(sb, &opts, 0, NULL);
+        error = security_sb_set_mnt_opts(sb, sec_opts, 0, NULL);
         if (error)
                 goto out_sb;
 
@@ -1295,13 +1293,13 @@ mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
                 "negative value (%lld)\n", type->name, sb->s_maxbytes);
 
         up_write(&sb->s_umount);
-        security_free_mnt_opts(&opts);
+        security_free_mnt_opts(&sec_opts);
         return root;
 out_sb:
         dput(root);
         deactivate_locked_super(sb);
 out_free_secdata:
-        security_free_mnt_opts(&opts);
+        security_free_mnt_opts(&sec_opts);
         return ERR_PTR(error);
 }