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, 30 insertions, 8 deletions

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 835cca277c2a..81a8112975d4 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -567,6 +567,19 @@ static void smack_sb_free_security(struct super_block *sb)
 	sb->s_security = NULL;
 }
 
+static void smack_free_mnt_opts(void *mnt_opts)
+{
+	struct security_mnt_opts *opts = mnt_opts;
+	int i;
+
+	if (opts->mnt_opts)
+		for (i = 0; i < opts->num_mnt_opts; i++)
+			kfree(opts->mnt_opts[i]);
+	kfree(opts->mnt_opts);
+	kfree(opts->mnt_opts_flags);
+	kfree(opts);
+}
+
 /**
  * smack_sb_copy_data - copy mount options data for processing
  * @orig: where to start
@@ -624,8 +637,9 @@ static int smack_sb_copy_data(char *orig, char *smackopts)
  * converts Smack specific mount options to generic security option format
  */
 static int smack_parse_opts_str(char *options,
-		struct security_mnt_opts *opts)
+		void **mnt_opts)
 {
+	struct security_mnt_opts *opts = *mnt_opts;
 	char *p;
 	char *fsdefault = NULL;
 	char *fsfloor = NULL;
@@ -636,11 +650,17 @@ static int smack_parse_opts_str(char *options,
 	int num_mnt_opts = 0;
 	int token;
 
-	opts->num_mnt_opts = 0;
-
 	if (!options)
 		return 0;
 
+	if (!opts) {
+		opts = kzalloc(sizeof(struct security_mnt_opts), GFP_KERNEL);
+		*mnt_opts = opts;
+		if (!opts)
+			return -ENOMEM;
+	}
+	opts->num_mnt_opts = 0;
+
 	while ((p = strsep(&options, ",")) != NULL) {
 		substring_t args[MAX_OPT_ARGS];
 
@@ -735,11 +755,11 @@ out_err:
 	kfree(fshat);
 	kfree(fsroot);
 	kfree(fstransmute);
-	security_free_mnt_opts(opts);
+	security_free_mnt_opts(mnt_opts);
 	return rc;
 }
 
-static int smack_sb_eat_lsm_opts(char *options, struct security_mnt_opts *opts)
+static int smack_sb_eat_lsm_opts(char *options, void **mnt_opts)
 {
 	char *s = (char *)get_zeroed_page(GFP_KERNEL);
 	int err;
@@ -748,7 +768,7 @@ static int smack_sb_eat_lsm_opts(char *options, struct security_mnt_opts *opts)
 		return -ENOMEM;
 	err = smack_sb_copy_data(options, s);
 	if (!err)
-		err = smack_parse_opts_str(s, opts);
+		err = smack_parse_opts_str(s, mnt_opts);
 	free_page((unsigned long)s);
 	return err;
 }
@@ -766,7 +786,7 @@ static int smack_sb_eat_lsm_opts(char *options, struct security_mnt_opts *opts)
  * labels.
  */
 static int smack_set_mnt_opts(struct super_block *sb,
-		struct security_mnt_opts *opts,
+		void *mnt_opts,
 		unsigned long kern_flags,
 		unsigned long *set_kern_flags)
 {
@@ -776,7 +796,8 @@ static int smack_set_mnt_opts(struct super_block *sb,
 	struct inode_smack *isp;
 	struct smack_known *skp;
 	int i;
-	int num_opts = opts->num_mnt_opts;
+	struct security_mnt_opts *opts = mnt_opts;
+	int num_opts = opts ? opts->num_mnt_opts : 0;
 	int transmute = 0;
 
 	if (sp->smk_flags & SMK_SB_INITIALIZED)
@@ -4651,6 +4672,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
 
 	LSM_HOOK_INIT(sb_alloc_security, smack_sb_alloc_security),
 	LSM_HOOK_INIT(sb_free_security, smack_sb_free_security),
+	LSM_HOOK_INIT(sb_free_mnt_opts, smack_free_mnt_opts),
 	LSM_HOOK_INIT(sb_eat_lsm_opts, smack_sb_eat_lsm_opts),
 	LSM_HOOK_INIT(sb_statfs, smack_sb_statfs),
 	LSM_HOOK_INIT(sb_set_mnt_opts, smack_set_mnt_opts),