LSM/SELinux: Interfaces to allow FS to control mount options

Introduce new LSM interfaces to allow an FS to deal with their own mount
options. This includes a new string parsing function exported from the
LSM that an FS can use to get a security data blob and a new security
data blob. This is particularly useful for an FS which uses binary
mount data, like NFS, which does not pass strings into the vfs to be
handled by the loaded LSM. Also fix a BUG() in both SELinux and SMACK
when dealing with binary mount data. If the binary mount data is less
than one page the copy_page() in security_sb_copy_data() can cause an
illegal page fault and boom. Remove all NFSisms from the SELinux code
since they were broken by past NFS changes.

Signed-off-by: Eric Paris <[e-mail]>
Acked-by: Stephen Smalley <[e-mail]>
Acked-by: Casey Schaufler <[e-mail]>
Signed-off-by: James Morris <[e-mail]>

fs/super.c

···
 	if (!mnt)
 		goto out;
 
-	if (data) {
+	if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
 		secdata = alloc_secdata();
 		if (!secdata)
 			goto out_mnt;
 
-		error = security_sb_copy_data(type, data, secdata);
+		error = security_sb_copy_data(data, secdata);
 		if (error)
 			goto out_free_secdata;
 	}

include/linux/security.h

···
 #include <linux/xfrm.h>
 #include <net/flow.h>
 
-/* only a char in selinux superblock security struct flags */
-#define FSCONTEXT_MNT		0x01
-#define CONTEXT_MNT		0x02
-#define ROOTCONTEXT_MNT		0x04
-#define DEFCONTEXT_MNT		0x08
-
 extern unsigned securebits;
 
 struct ctl_table;
···
 #define LSM_UNSAFE_PTRACE_CAP	4
 
 #ifdef CONFIG_SECURITY
+
+struct security_mnt_opts {
+	char **mnt_opts;
+	int *mnt_opts_flags;
+	int num_mnt_opts;
+};
+
+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;
+}
 
 /**
  * struct security_operations - main security structure
···
  * @sb_get_mnt_opts:
  *	Get the security relevant mount options used for a superblock
  *	@sb the superblock to get security mount options from
- *	@mount_options array for pointers to mount options
- *	@mount_flags array of ints specifying what each mount options is
- *	@num_opts number of options in the arrays
+ *	@opts binary data structure containing all lsm mount data
  * @sb_set_mnt_opts:
  *	Set the security relevant mount options used for a superblock
  *	@sb the superblock to set security mount options for
- *	@mount_options array for pointers to mount options
- *	@mount_flags array of ints specifying what each mount options is
- *	@num_opts number of options in the arrays
+ *	@opts binary data structure containing all lsm mount data
  * @sb_clone_mnt_opts:
  *	Copy all security options from a given superblock to another
  *	@oldsb old superblock which contain information to clone
  *	@newsb new superblock which needs filled in
+ * @sb_parse_opts_str:
+ *	Parse a string of security data filling in the opts structure
+ *	@options string containing all mount options known by the LSM
+ *	@opts binary data structure usable by the LSM
  *
  * Security hooks for inode operations.
  *
···
 
 	int (*sb_alloc_security) (struct super_block * sb);
 	void (*sb_free_security) (struct super_block * sb);
-	int (*sb_copy_data)(struct file_system_type *type,
-			    void *orig, void *copy);
+	int (*sb_copy_data)(char *orig, char *copy);
 	int (*sb_kern_mount) (struct super_block *sb, void *data);
 	int (*sb_statfs) (struct dentry *dentry);
 	int (*sb_mount) (char *dev_name, struct nameidata * nd,
···
 	void (*sb_post_pivotroot) (struct nameidata * old_nd,
 				   struct nameidata * new_nd);
 	int (*sb_get_mnt_opts) (const struct super_block *sb,
-				char ***mount_options, int **flags,
-				int *num_opts);
-	int (*sb_set_mnt_opts) (struct super_block *sb, char **mount_options,
-				int *flags, int num_opts);
+				struct security_mnt_opts *opts);
+	int (*sb_set_mnt_opts) (struct super_block *sb,
+				struct security_mnt_opts *opts);
 	void (*sb_clone_mnt_opts) (const struct super_block *oldsb,
 				   struct super_block *newsb);
+	int (*sb_parse_opts_str) (char *options, struct security_mnt_opts *opts);
 
 	int (*inode_alloc_security) (struct inode *inode);	
 	void (*inode_free_security) (struct inode *inode);
···
 int security_bprm_secureexec(struct linux_binprm *bprm);
 int security_sb_alloc(struct super_block *sb);
 void security_sb_free(struct super_block *sb);
-int security_sb_copy_data(struct file_system_type *type, void *orig, void *copy);
+int security_sb_copy_data(char *orig, char *copy);
 int security_sb_kern_mount(struct super_block *sb, void *data);
 int security_sb_statfs(struct dentry *dentry);
 int security_sb_mount(char *dev_name, struct nameidata *nd,
···
 void security_sb_post_addmount(struct vfsmount *mnt, struct nameidata *mountpoint_nd);
 int security_sb_pivotroot(struct nameidata *old_nd, struct nameidata *new_nd);
 void security_sb_post_pivotroot(struct nameidata *old_nd, struct nameidata *new_nd);
-int security_sb_get_mnt_opts(const struct super_block *sb, char ***mount_options,
-			     int **flags, int *num_opts);
-int security_sb_set_mnt_opts(struct super_block *sb, char **mount_options,
-			     int *flags, int num_opts);
+int security_sb_get_mnt_opts(const struct super_block *sb,
+				struct security_mnt_opts *opts);
+int security_sb_set_mnt_opts(struct super_block *sb, struct security_mnt_opts *opts);
 void security_sb_clone_mnt_opts(const struct super_block *oldsb,
 				struct super_block *newsb);
+int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
 
 int security_inode_alloc(struct inode *inode);
 void security_inode_free(struct inode *inode);
···
 void security_release_secctx(char *secdata, u32 seclen);
 
 #else /* CONFIG_SECURITY */
+struct security_mnt_opts {
+};
+
+static inline void security_init_mnt_opts(struct security_mnt_opts *opts)
+{
+}
+
+static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
+{
+}
 
 /*
  * This is the default capabilities functionality.  Most of these functions
···
 static inline void security_sb_free (struct super_block *sb)
 { }
 
-static inline int security_sb_copy_data (struct file_system_type *type,
-					 void *orig, void *copy)
+static inline int security_sb_copy_data (char *orig, char *copy)
 {
 	return 0;
 }
···
 static inline void security_sb_post_pivotroot (struct nameidata *old_nd,
 					       struct nameidata *new_nd)
 { }
+static inline int security_sb_get_mnt_opts(const struct super_block *sb,
+					   struct security_mnt_opts *opts)
+{
+	security_init_mnt_opts(opts);
+	return 0;
+}
+
+static inline int security_sb_set_mnt_opts(struct super_block *sb,
+					   struct security_mnt_opts *opts)
+{
+	return 0;
+}
+
+static inline void security_sb_clone_mnt_opts(const struct super_block *oldsb,
+					      struct super_block *newsb)
+{ }
+
+static inline int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
+{
+	return 0;
+}
 
 static inline int security_inode_alloc (struct inode *inode)
 {

security/dummy.c

···
 	return;
 }
 
-static int dummy_sb_copy_data (struct file_system_type *type,
-			       void *orig, void *copy)
+static int dummy_sb_copy_data (char *orig, char *copy)
 {
 	return 0;
 }
···
 	return;
 }
 
-static int dummy_sb_get_mnt_opts(const struct super_block *sb, char ***mount_options,
-				 int **flags, int *num_opts)
+static int dummy_sb_get_mnt_opts(const struct super_block *sb,
+				 struct security_mnt_opts *opts)
 {
-	*mount_options = NULL;
-	*flags = NULL;
-	*num_opts = 0;
+	security_init_mnt_opts(opts);
 	return 0;
 }
 
-static int dummy_sb_set_mnt_opts(struct super_block *sb, char **mount_options,
-				 int *flags, int num_opts)
+static int dummy_sb_set_mnt_opts(struct super_block *sb,
+				 struct security_mnt_opts *opts)
 {
-	if (unlikely(num_opts))
+	if (unlikely(opts->num_mnt_opts))
 		return -EOPNOTSUPP;
 	return 0;
 }
···
 				    struct super_block *newsb)
 {
 	return;
+}
+
+static int dummy_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
+{
+	return 0;
 }
 
 static int dummy_inode_alloc_security (struct inode *inode)
···
 	set_to_dummy_if_null(ops, sb_get_mnt_opts);
 	set_to_dummy_if_null(ops, sb_set_mnt_opts);
 	set_to_dummy_if_null(ops, sb_clone_mnt_opts);
+	set_to_dummy_if_null(ops, sb_parse_opts_str);
 	set_to_dummy_if_null(ops, inode_alloc_security);
 	set_to_dummy_if_null(ops, inode_free_security);
 	set_to_dummy_if_null(ops, inode_init_security);

security/security.c

···
 	security_ops->sb_free_security(sb);
 }
 
-int security_sb_copy_data(struct file_system_type *type, void *orig, void *copy)
+int security_sb_copy_data(char *orig, char *copy)
 {
-	return security_ops->sb_copy_data(type, orig, copy);
+	return security_ops->sb_copy_data(orig, copy);
 }
+EXPORT_SYMBOL(security_sb_copy_data);
 
 int security_sb_kern_mount(struct super_block *sb, void *data)
 {
···
 }
 
 int security_sb_get_mnt_opts(const struct super_block *sb,
-			      char ***mount_options,
-			      int **flags, int *num_opts)
+				struct security_mnt_opts *opts)
 {
-	return security_ops->sb_get_mnt_opts(sb, mount_options, flags, num_opts);
+	return security_ops->sb_get_mnt_opts(sb, opts);
 }
 
 int security_sb_set_mnt_opts(struct super_block *sb,
-			      char **mount_options,
-			      int *flags, int num_opts)
+				struct security_mnt_opts *opts)
 {
-	return security_ops->sb_set_mnt_opts(sb, mount_options, flags, num_opts);
+	return security_ops->sb_set_mnt_opts(sb, opts);
 }
+EXPORT_SYMBOL(security_sb_set_mnt_opts);
 
 void security_sb_clone_mnt_opts(const struct super_block *oldsb,
 				struct super_block *newsb)
 {
 	security_ops->sb_clone_mnt_opts(oldsb, newsb);
 }
+EXPORT_SYMBOL(security_sb_clone_mnt_opts);
+
+int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
+{
+	return security_ops->sb_parse_opts_str(options, opts);
+}
+EXPORT_SYMBOL(security_sb_parse_opts_str);
 
 int security_inode_alloc(struct inode *inode)
 {

security/selinux/hooks.c

···
  * mount options, or whatever.
  */
 static int selinux_get_mnt_opts(const struct super_block *sb,
-				char ***mount_options, int **mnt_opts_flags,
-				int *num_opts)
+				struct security_mnt_opts *opts)
 {
 	int rc = 0, i;
 	struct superblock_security_struct *sbsec = sb->s_security;
···
 	u32 len;
 	char tmp;
 
-	*num_opts = 0;
-	*mount_options = NULL;
-	*mnt_opts_flags = NULL;
+	security_init_mnt_opts(opts);
 
 	if (!sbsec->initialized)
 		return -EINVAL;
···
 	/* count the number of mount options for this sb */
 	for (i = 0; i < 8; i++) {
 		if (tmp & 0x01)
-			(*num_opts)++;
+			opts->num_mnt_opts++;
 		tmp >>= 1;
 	}
 
-	*mount_options = kcalloc(*num_opts, sizeof(char *), GFP_ATOMIC);
-	if (!*mount_options) {
+	opts->mnt_opts = kcalloc(opts->num_mnt_opts, sizeof(char *), GFP_ATOMIC);
+	if (!opts->mnt_opts) {
 		rc = -ENOMEM;
 		goto out_free;
 	}
 
-	*mnt_opts_flags = kcalloc(*num_opts, sizeof(int), GFP_ATOMIC);
-	if (!*mnt_opts_flags) {
+	opts->mnt_opts_flags = kcalloc(opts->num_mnt_opts, sizeof(int), GFP_ATOMIC);
+	if (!opts->mnt_opts_flags) {
 		rc = -ENOMEM;
 		goto out_free;
 	}
···
 		rc = security_sid_to_context(sbsec->sid, &context, &len);
 		if (rc)
 			goto out_free;
-		(*mount_options)[i] = context;
-		(*mnt_opts_flags)[i++] = FSCONTEXT_MNT;
+		opts->mnt_opts[i] = context;
+		opts->mnt_opts_flags[i++] = FSCONTEXT_MNT;
 	}
 	if (sbsec->flags & CONTEXT_MNT) {
 		rc = security_sid_to_context(sbsec->mntpoint_sid, &context, &len);
 		if (rc)
 			goto out_free;
-		(*mount_options)[i] = context;
-		(*mnt_opts_flags)[i++] = CONTEXT_MNT;
+		opts->mnt_opts[i] = context;
+		opts->mnt_opts_flags[i++] = CONTEXT_MNT;
 	}
 	if (sbsec->flags & DEFCONTEXT_MNT) {
 		rc = security_sid_to_context(sbsec->def_sid, &context, &len);
 		if (rc)
 			goto out_free;
-		(*mount_options)[i] = context;
-		(*mnt_opts_flags)[i++] = DEFCONTEXT_MNT;
+		opts->mnt_opts[i] = context;
+		opts->mnt_opts_flags[i++] = DEFCONTEXT_MNT;
 	}
 	if (sbsec->flags & ROOTCONTEXT_MNT) {
 		struct inode *root = sbsec->sb->s_root->d_inode;
···
 		rc = security_sid_to_context(isec->sid, &context, &len);
 		if (rc)
 			goto out_free;
-		(*mount_options)[i] = context;
-		(*mnt_opts_flags)[i++] = ROOTCONTEXT_MNT;
+		opts->mnt_opts[i] = context;
+		opts->mnt_opts_flags[i++] = ROOTCONTEXT_MNT;
 	}
 
-	BUG_ON(i != *num_opts);
+	BUG_ON(i != opts->num_mnt_opts);
 
 	return 0;
 
 out_free:
-	/* don't leak context string if security_sid_to_context had an error */
-	if (*mount_options && i)
-		for (; i > 0; i--)
-			kfree((*mount_options)[i-1]);
-	kfree(*mount_options);
-	*mount_options = NULL;
-	kfree(*mnt_opts_flags);
-	*mnt_opts_flags = NULL;
-	*num_opts = 0;
+	security_free_mnt_opts(opts);
 	return rc;
 }
 
···
 			return 1;
 	return 0;
 }
+
 /*
  * Allow filesystems with binary mount data to explicitly set mount point
  * labeling information.
  */
-static int selinux_set_mnt_opts(struct super_block *sb, char **mount_options,
-				int *flags, int num_opts)
+static int selinux_set_mnt_opts(struct super_block *sb,
+				struct security_mnt_opts *opts)
 {
 	int rc = 0, i;
 	struct task_security_struct *tsec = current->security;
···
 	struct inode_security_struct *root_isec = inode->i_security;
 	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;
 
 	mutex_lock(&sbsec->lock);
 
···
 		       "the security server is initialized\n");
 		goto out;
 	}
+
+	/*
+	 * Binary mount data FS will come through this function twice.  Once
+	 * from an explicit call and once from the generic calls from the vfs.
+	 * Since the generic VFS calls will not contain any security mount data
+	 * we need to skip the double mount verification.
+	 *
+	 * This does open a hole in which we will not notice if the first
+	 * mount using this sb set explict options and a second mount using
+	 * this sb does not set any security options.  (The first options
+	 * will be used for both mounts)
+	 */
+	if (sbsec->initialized && (sb->s_type->fs_flags & FS_BINARY_MOUNTDATA)
+	    && (num_opts == 0))
+	        goto out;
 
 	/*
 	 * parse the mount options, check if they are valid sids.
···
 	mutex_unlock(&newsbsec->lock);
 }
 
-/*
- * string mount options parsing and call set the sbsec
- */
-static int superblock_doinit(struct super_block *sb, void *data)
+int selinux_parse_opts_str(char *options, struct security_mnt_opts *opts)
 {
+	char *p;
 	char *context = NULL, *defcontext = NULL;
 	char *fscontext = NULL, *rootcontext = NULL;
-	int rc = 0;
-	char *p, *options = data;
-	/* selinux only know about a fixed number of mount options */
-	char *mnt_opts[NUM_SEL_MNT_OPTS];
-	int mnt_opts_flags[NUM_SEL_MNT_OPTS], num_mnt_opts = 0;
+	int rc, num_mnt_opts = 0;
 
-	if (!data)
-		goto out;
-
-	/* with the nfs patch this will become a goto out; */
-	if (sb->s_type->fs_flags & FS_BINARY_MOUNTDATA) {
-		const char *name = sb->s_type->name;
-		/* NFS we understand. */
-		if (!strcmp(name, "nfs")) {
-			struct nfs_mount_data *d = data;
-
-			if (d->version !=  NFS_MOUNT_VERSION)
-				goto out;
-
-			if (d->context[0]) {
-				context = kstrdup(d->context, GFP_KERNEL);
-				if (!context) {
-					rc = -ENOMEM;
-					goto out;
-				}
-			}
-			goto build_flags;
-		} else
-			goto out;
-	}
+	opts->num_mnt_opts = 0;
 
 	/* Standard string-based options. */
 	while ((p = strsep(&options, "|")) != NULL) {
···
 		}
 	}
 
-build_flags:
-	if (fscontext) {
-		mnt_opts[num_mnt_opts] = fscontext;
-		mnt_opts_flags[num_mnt_opts++] = FSCONTEXT_MNT;
-	}
-	if (context) {
-		mnt_opts[num_mnt_opts] = context;
-		mnt_opts_flags[num_mnt_opts++] = CONTEXT_MNT;
-	}
-	if (rootcontext) {
-		mnt_opts[num_mnt_opts] = rootcontext;
-		mnt_opts_flags[num_mnt_opts++] = ROOTCONTEXT_MNT;
-	}
-	if (defcontext) {
-		mnt_opts[num_mnt_opts] = defcontext;
-		mnt_opts_flags[num_mnt_opts++] = DEFCONTEXT_MNT;
+	rc = -ENOMEM;
+	opts->mnt_opts = kcalloc(NUM_SEL_MNT_OPTS, sizeof(char *), GFP_ATOMIC);
+	if (!opts->mnt_opts)
+		goto out_err;
+
+	opts->mnt_opts_flags = kcalloc(NUM_SEL_MNT_OPTS, sizeof(int), GFP_ATOMIC);
+	if (!opts->mnt_opts_flags) {
+		kfree(opts->mnt_opts);
+		goto out_err;
 	}
 
-out:
-	rc = selinux_set_mnt_opts(sb, mnt_opts, mnt_opts_flags, num_mnt_opts);
+	if (fscontext) {
+		opts->mnt_opts[num_mnt_opts] = fscontext;
+		opts->mnt_opts_flags[num_mnt_opts++] = FSCONTEXT_MNT;
+	}
+	if (context) {
+		opts->mnt_opts[num_mnt_opts] = context;
+		opts->mnt_opts_flags[num_mnt_opts++] = CONTEXT_MNT;
+	}
+	if (rootcontext) {
+		opts->mnt_opts[num_mnt_opts] = rootcontext;
+		opts->mnt_opts_flags[num_mnt_opts++] = ROOTCONTEXT_MNT;
+	}
+	if (defcontext) {
+		opts->mnt_opts[num_mnt_opts] = defcontext;
+		opts->mnt_opts_flags[num_mnt_opts++] = DEFCONTEXT_MNT;
+	}
+
+	opts->num_mnt_opts = num_mnt_opts;
+	return 0;
+
 out_err:
 	kfree(context);
 	kfree(defcontext);
 	kfree(fscontext);
 	kfree(rootcontext);
+	return rc;
+}
+/*
+ * string mount options parsing and call set the sbsec
+ */
+static int superblock_doinit(struct super_block *sb, void *data)
+{
+	int rc = 0;
+	char *options = data;
+	struct security_mnt_opts opts;
+
+	security_init_mnt_opts(&opts);
+
+	if (!data)
+		goto out;
+
+	BUG_ON(sb->s_type->fs_flags & FS_BINARY_MOUNTDATA);
+
+	rc = selinux_parse_opts_str(options, &opts);
+	if (rc)
+		goto out_err;
+
+out:
+	rc = selinux_set_mnt_opts(sb, &opts);
+
+out_err:
+	security_free_mnt_opts(&opts);
 	return rc;
 }
 
···
 	}
 }
 
-static int selinux_sb_copy_data(struct file_system_type *type, void *orig, void *copy)
+static int selinux_sb_copy_data(char *orig, char *copy)
 {
 	int fnosec, fsec, rc = 0;
 	char *in_save, *in_curr, *in_end;
···
 
 	in_curr = orig;
 	sec_curr = copy;
-
-	/* Binary mount data: just copy */
-	if (type->fs_flags & FS_BINARY_MOUNTDATA) {
-		copy_page(sec_curr, in_curr);
-		goto out;
-	}
 
 	nosec = (char *)get_zeroed_page(GFP_KERNEL);
 	if (!nosec) {
···
 	.sb_get_mnt_opts =		selinux_get_mnt_opts,
 	.sb_set_mnt_opts =		selinux_set_mnt_opts,
 	.sb_clone_mnt_opts = 		selinux_sb_clone_mnt_opts,
+	.sb_parse_opts_str = 		selinux_parse_opts_str,
+
 
 	.inode_alloc_security =		selinux_inode_alloc_security,
 	.inode_free_security =		selinux_inode_free_security,

security/selinux/include/security.h

···
 #define POLICYDB_VERSION_MAX	POLICYDB_VERSION_POLCAP
 #endif
 
+#define CONTEXT_MNT	0x01
+#define FSCONTEXT_MNT	0x02
+#define ROOTCONTEXT_MNT	0x04
+#define DEFCONTEXT_MNT	0x08
+
 struct netlbl_lsm_secattr;
 
 extern int selinux_enabled;

security/smack/smack_lsm.c

···
  * Copy the Smack specific mount options out of the mount
  * options list.
  */
-static int smack_sb_copy_data(struct file_system_type *type, void *orig,
-			      void *smackopts)
+static int smack_sb_copy_data(char *orig, char *smackopts)
 {
 	char *cp, *commap, *otheropts, *dp;
-
-	/* Binary mount data: just copy */
-	if (type->fs_flags & FS_BINARY_MOUNTDATA) {
-		copy_page(smackopts, orig);
-		return 0;
-	}
 
 	otheropts = (char *)get_zeroed_page(GFP_KERNEL);
 	if (otheropts == NULL)