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 <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

fs/btrfs/super.c

···
 	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)
···
 		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);
···
 	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;

fs/namespace.c

···
 	int err;
 	struct super_block *sb = path->mnt->mnt_sb;
 	struct mount *mnt = real_mount(path->mnt);
-	struct security_mnt_opts opts;
+	void *sec_opts = NULL;
 
 	if (!check_mnt(mnt))
 		return -EINVAL;
···
 	if (!can_change_locked_flags(mnt, mnt_flags))
 		return -EPERM;
 
-	security_init_mnt_opts(&opts);
 	if (data && !(sb->s_type->fs_flags & FS_BINARY_MOUNTDATA)) {
-		err = security_sb_eat_lsm_opts(data, &opts);
+		err = security_sb_eat_lsm_opts(data, &sec_opts);
 		if (err)
 			return err;
 	}
-	err = security_sb_remount(sb, &opts);
-	security_free_mnt_opts(&opts);
+	err = security_sb_remount(sb, sec_opts);
+	security_free_mnt_opts(&sec_opts);
 	if (err)
 		return err;
 

fs/nfs/internal.h

···
 		unsigned short		protocol;
 	} nfs_server;
 
-	struct security_mnt_opts lsm_opts;
+	void			*lsm_opts;
 	struct net		*net;
 };
 

fs/nfs/super.c

···
 		data->minorversion	= 0;
 		data->need_mount	= true;
 		data->net		= current->nsproxy->net_ns;
-		security_init_mnt_opts(&data->lsm_opts);
+		data->lsm_opts		= NULL;
 	}
 	return data;
 }
···
 	/* compare new mount options with old ones */
 	error = nfs_compare_remount_data(nfss, data);
 	if (!error)
-		error = security_sb_remount(sb, &data->lsm_opts);
+		error = security_sb_remount(sb, data->lsm_opts);
 out:
 	nfs_free_parsed_mount_data(data);
 	return error;
···
 	if (NFS_SB(s)->caps & NFS_CAP_SECURITY_LABEL)
 		kflags |= SECURITY_LSM_NATIVE_LABELS;
 
-	error = security_sb_set_mnt_opts(s, &mount_info->parsed->lsm_opts,
+	error = security_sb_set_mnt_opts(s, mount_info->parsed->lsm_opts,
 						kflags, &kflags_out);
 	if (error)
 		goto err;

fs/super.c

···
 	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);
 	}
···
 	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;
 
···
 		"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);
 }
 

include/linux/lsm_hooks.h

···
 
 	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);
···
 	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);
···
 	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;

include/linux/security.h

···
 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);
 
···
 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);
···
 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);
···
 	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)
 {
 }
 
···
 { }
 
 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;
 }
···
 }
 
 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)
 {
···
 	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;
 }

security/security.c

···
 	call_void_hook(sb_free_security, sb);
 }
 
-int security_sb_eat_lsm_opts(char *options, struct security_mnt_opts *opts)
+void security_free_mnt_opts(void **mnt_opts)
 {
-	return call_int_hook(sb_eat_lsm_opts, 0, options, opts);
+	if (!*mnt_opts)
+		return;
+	call_void_hook(sb_free_mnt_opts, *mnt_opts);
+	*mnt_opts = NULL;
+}
+EXPORT_SYMBOL(security_free_mnt_opts);
+
+int security_sb_eat_lsm_opts(char *options, void **mnt_opts)
+{
+	return call_int_hook(sb_eat_lsm_opts, 0, options, mnt_opts);
 }
 EXPORT_SYMBOL(security_sb_eat_lsm_opts);
 
 int security_sb_remount(struct super_block *sb,
-			struct security_mnt_opts *opts)
+			void *mnt_opts)
 {
-	return call_int_hook(sb_remount, 0, sb, opts);
+	return call_int_hook(sb_remount, 0, sb, mnt_opts);
 }
 EXPORT_SYMBOL(security_sb_remount);
 
···
 }
 
 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)
 {
 	return call_int_hook(sb_set_mnt_opts,
-				opts->num_mnt_opts ? -EOPNOTSUPP : 0, sb,
-				opts, kern_flags, set_kern_flags);
+				mnt_opts ? -EOPNOTSUPP : 0, sb,
+				mnt_opts, kern_flags, set_kern_flags);
 }
 EXPORT_SYMBOL(security_sb_set_mnt_opts);
 
···
 }
 EXPORT_SYMBOL(security_sb_clone_mnt_opts);
 
-int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
+int security_sb_parse_opts_str(char *options, void **mnt_opts)
 {
-	return call_int_hook(sb_parse_opts_str, 0, options, opts);
+	return call_int_hook(sb_parse_opts_str, 0, options, mnt_opts);
 }
 EXPORT_SYMBOL(security_sb_parse_opts_str);
 

security/selinux/hooks.c

···
 	kfree(sbsec);
 }
 
+static void selinux_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);
+}
+
 static inline int inode_doinit(struct inode *inode)
 {
 	return inode_doinit_with_dentry(inode, NULL);
···
  * labeling information.
  */
 static int selinux_set_mnt_opts(struct super_block *sb,
-				struct security_mnt_opts *opts,
+				void *mnt_opts,
 				unsigned long kern_flags,
 				unsigned long *set_kern_flags)
 {
···
 	struct inode_security_struct *root_isec;
 	u32 fscontext_sid = 0, context_sid = 0, rootcontext_sid = 0;
 	u32 defcontext_sid = 0;
-	char **mount_options = opts->mnt_opts;
-	int *flags = opts->mnt_opts_flags;
-	int num_opts = opts->num_mnt_opts;
+	struct security_mnt_opts *opts = mnt_opts;
+	char **mount_options = opts ? opts->mnt_opts : NULL;
+	int *flags = opts ? opts->mnt_opts_flags : NULL;
+	int num_opts = opts ? opts->num_mnt_opts : 0;
 
 	mutex_lock(&sbsec->lock);
 
···
 }
 
 static int selinux_parse_opts_str(char *options,
-				  struct security_mnt_opts *opts)
+				  void **mnt_opts)
 {
 	char *p;
 	char *context = NULL, *defcontext = NULL;
 	char *fscontext = NULL, *rootcontext = NULL;
 	int rc, num_mnt_opts = 0;
+	struct security_mnt_opts *opts = *mnt_opts;
+
+	if (!opts) {
+		opts = kzalloc(sizeof(struct security_mnt_opts), GFP_KERNEL);
+		*mnt_opts = opts;
+		if (!opts)
+			return -ENOMEM;
+	}
 
 	opts->num_mnt_opts = 0;
 
···
 	return 0;
 
 out_err:
-	security_free_mnt_opts(opts);
+	security_free_mnt_opts(mnt_opts);
 	kfree(context);
 	kfree(defcontext);
 	kfree(fscontext);
···
 	return rc;
 }
 
-static int selinux_sb_eat_lsm_opts(char *options, struct security_mnt_opts *opts)
+static int selinux_sb_eat_lsm_opts(char *options, void **mnt_opts)
 {
 	char *s = (char *)get_zeroed_page(GFP_KERNEL);
 	int err;
···
 		return -ENOMEM;
 	err = selinux_sb_copy_data(options, s);
 	if (!err)
-		err = selinux_parse_opts_str(s, opts);
+		err = selinux_parse_opts_str(s, mnt_opts);
 	free_page((unsigned long)s);
 	return err;
 }
 
-static int selinux_sb_remount(struct super_block *sb,
-			      struct security_mnt_opts *opts)
+static int selinux_sb_remount(struct super_block *sb, void *mnt_opts)
 {
+	struct security_mnt_opts *opts = mnt_opts;
 	int i, *flags;
 	char **mount_options;
 	struct superblock_security_struct *sbsec = sb->s_security;
 
 	if (!(sbsec->flags & SE_SBINITIALIZED))
+		return 0;
+
+	if (!opts)
 		return 0;
 
 	mount_options = opts->mnt_opts;
···
 	LSM_HOOK_INIT(sb_alloc_security, selinux_sb_alloc_security),
 	LSM_HOOK_INIT(sb_free_security, selinux_sb_free_security),
 	LSM_HOOK_INIT(sb_eat_lsm_opts, selinux_sb_eat_lsm_opts),
+	LSM_HOOK_INIT(sb_free_mnt_opts, selinux_free_mnt_opts),
 	LSM_HOOK_INIT(sb_remount, selinux_sb_remount),
 	LSM_HOOK_INIT(sb_kern_mount, selinux_sb_kern_mount),
 	LSM_HOOK_INIT(sb_show_options, selinux_sb_show_options),
···
 
 static void delayed_superblock_init(struct super_block *sb, void *unused)
 {
-	struct security_mnt_opts opts;
-
-	security_init_mnt_opts(&opts);
-	selinux_set_mnt_opts(sb, &opts, 0, NULL);
-	security_free_mnt_opts(&opts);
+	selinux_set_mnt_opts(sb, NULL, 0, NULL);
 }
 
 void selinux_complete_init(void)

security/smack/smack_lsm.c

···
 	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
···
  * 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;
···
 	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];
···
 	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;
···
 		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;
 }
···
  * 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)
 {
···
 	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)
···
 
 	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),