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>

2 files changed, 16 insertions, 38 deletions

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index c418909c178c..a9c541f5732e 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1461,9 +1461,9 @@ union security_list_options {
 
 	int (*sb_alloc_security)(struct super_block *sb);
 	void (*sb_free_security)(struct super_block *sb);
-	int (*sb_eat_lsm_opts)(char *orig, struct security_mnt_opts *opts);
-	int (*sb_remount)(struct super_block *sb,
-			  struct security_mnt_opts *opts);
+	void (*sb_free_mnt_opts)(void *mnt_opts);
+	int (*sb_eat_lsm_opts)(char *orig, void **mnt_opts);
+	int (*sb_remount)(struct super_block *sb, void *mnt_opts);
 	int (*sb_kern_mount)(struct super_block *sb);
 	int (*sb_show_options)(struct seq_file *m, struct super_block *sb);
 	int (*sb_statfs)(struct dentry *dentry);
@@ -1472,14 +1472,14 @@ union security_list_options {
 	int (*sb_umount)(struct vfsmount *mnt, int flags);
 	int (*sb_pivotroot)(const struct path *old_path, const struct path *new_path);
 	int (*sb_set_mnt_opts)(struct super_block *sb,
-				struct security_mnt_opts *opts,
+				void *mnt_opts,
 				unsigned long kern_flags,
 				unsigned long *set_kern_flags);
 	int (*sb_clone_mnt_opts)(const struct super_block *oldsb,
 					struct super_block *newsb,
 					unsigned long kern_flags,
 					unsigned long *set_kern_flags);
-	int (*sb_parse_opts_str)(char *options, struct security_mnt_opts *opts);
+	int (*sb_parse_opts_str)(char *options, void **mnt_opts);
 	int (*dentry_init_security)(struct dentry *dentry, int mode,
 					const struct qstr *name, void **ctx,
 					u32 *ctxlen);
@@ -1801,6 +1801,7 @@ struct security_hook_heads {
 	struct hlist_head bprm_committed_creds;
 	struct hlist_head sb_alloc_security;
 	struct hlist_head sb_free_security;
+	struct hlist_head sb_free_mnt_opts;
 	struct hlist_head sb_eat_lsm_opts;
 	struct hlist_head sb_remount;
 	struct hlist_head sb_kern_mount;
diff --git a/include/linux/security.h b/include/linux/security.h
index d00093363570..4bca0be95b7a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -192,26 +192,6 @@ int call_lsm_notifier(enum lsm_event event, void *data);
 int register_lsm_notifier(struct notifier_block *nb);
 int unregister_lsm_notifier(struct notifier_block *nb);
 
-static inline void security_init_mnt_opts(struct security_mnt_opts *opts)
-{
-	opts->mnt_opts = NULL;
-	opts->mnt_opts_flags = NULL;
-	opts->num_mnt_opts = 0;
-}
-
-static inline void security_free_mnt_opts(struct security_mnt_opts *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);
-	opts->mnt_opts = NULL;
-	kfree(opts->mnt_opts_flags);
-	opts->mnt_opts_flags = NULL;
-	opts->num_mnt_opts = 0;
-}
-
 /* prototypes */
 extern int security_init(void);
 
@@ -248,8 +228,9 @@ void security_bprm_committing_creds(struct linux_binprm *bprm);
 void security_bprm_committed_creds(struct linux_binprm *bprm);
 int security_sb_alloc(struct super_block *sb);
 void security_sb_free(struct super_block *sb);
-int security_sb_eat_lsm_opts(char *options, struct security_mnt_opts *opts);
-int security_sb_remount(struct super_block *sb, struct security_mnt_opts *opts);
+void security_free_mnt_opts(void **mnt_opts);
+int security_sb_eat_lsm_opts(char *options, void **mnt_opts);
+int security_sb_remount(struct super_block *sb, void *mnt_opts);
 int security_sb_kern_mount(struct super_block *sb);
 int security_sb_show_options(struct seq_file *m, struct super_block *sb);
 int security_sb_statfs(struct dentry *dentry);
@@ -258,14 +239,14 @@ int security_sb_mount(const char *dev_name, const struct path *path,
 int security_sb_umount(struct vfsmount *mnt, int flags);
 int security_sb_pivotroot(const struct path *old_path, const struct path *new_path);
 int security_sb_set_mnt_opts(struct super_block *sb,
-				struct security_mnt_opts *opts,
+				void *mnt_opts,
 				unsigned long kern_flags,
 				unsigned long *set_kern_flags);
 int security_sb_clone_mnt_opts(const struct super_block *oldsb,
 				struct super_block *newsb,
 				unsigned long kern_flags,
 				unsigned long *set_kern_flags);
-int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
+int security_sb_parse_opts_str(char *options, void **mnt_opts);
 int security_dentry_init_security(struct dentry *dentry, int mode,
 					const struct qstr *name, void **ctx,
 					u32 *ctxlen);
@@ -421,11 +402,7 @@ static inline  int unregister_lsm_notifier(struct notifier_block *nb)
 	return 0;
 }
 
-static inline void security_init_mnt_opts(struct security_mnt_opts *opts)
-{
-}
-
-static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
+static inline void security_free_mnt_opts(void **mnt_opts)
 {
 }
 
@@ -556,13 +533,13 @@ static inline void security_sb_free(struct super_block *sb)
 { }
 
 static inline int security_sb_eat_lsm_opts(char *options,
-					   struct security_mnt_opts *opts)
+					   void **mnt_opts)
 {
 	return 0;
 }
 
 static inline int security_sb_remount(struct super_block *sb,
-				      struct security_mnt_opts *opts)
+				      void *mnt_opts)
 {
 	return 0;
 }
@@ -602,7 +579,7 @@ static inline int security_sb_pivotroot(const struct path *old_path,
 }
 
 static inline int security_sb_set_mnt_opts(struct super_block *sb,
-					   struct security_mnt_opts *opts,
+					   void *mnt_opts,
 					   unsigned long kern_flags,
 					   unsigned long *set_kern_flags)
 {
@@ -617,7 +594,7 @@ static inline int security_sb_clone_mnt_opts(const struct super_block *oldsb,
 	return 0;
 }
 
-static inline int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
+static inline int security_sb_parse_opts_str(char *options, void **mnt_opts)
 {
 	return 0;
 }