fs: add anon_inode_getfile_secure() similar to anon_inode_getfd_secure()

Extending the secure anonymous inode support to other subsystems
requires that we have a secure anon_inode_getfile() variant in
addition to the existing secure anon_inode_getfd() variant.

Thankfully we can reuse the existing __anon_inode_getfile() function
and just wrap it with the proper arguments.

Acked-by: Mickaël Salaün <mic@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

fs/anon_inodes.c

@@ -148,6 +148,35 @@ struct file *anon_inode_getfile(const char *name,
 }
 EXPORT_SYMBOL_GPL(anon_inode_getfile);
 
+/**
+ * anon_inode_getfile_secure - Like anon_inode_getfile(), but creates a new
+ *                             !S_PRIVATE anon inode rather than reuse the
+ *                             singleton anon inode and calls the
+ *                             inode_init_security_anon() LSM hook.  This
+ *                             allows for both the inode to have its own
+ *                             security context and for the LSM to enforce
+ *                             policy on the inode's creation.
+ *
+ * @name:    [in]    name of the "class" of the new file
+ * @fops:    [in]    file operations for the new file
+ * @priv:    [in]    private data for the new file (will be file's private_data)
+ * @flags:   [in]    flags
+ * @context_inode:
+ *           [in]    the logical relationship with the new inode (optional)
+ *
+ * The LSM may use @context_inode in inode_init_security_anon(), but a
+ * reference to it is not held.  Returns the newly created file* or an error
+ * pointer.  See the anon_inode_getfile() documentation for more information.
+ */
+struct file *anon_inode_getfile_secure(const char *name,
+				       const struct file_operations *fops,
+				       void *priv, int flags,
+				       const struct inode *context_inode)
+{
+	return __anon_inode_getfile(name, fops, priv, flags,
+				    context_inode, true);
+}
+
 static int __anon_inode_getfd(const char *name,
 			      const struct file_operations *fops,
 			      void *priv, int flags,

include/linux/anon_inodes.h

@@ -15,6 +15,10 @@ struct inode;
 struct file *anon_inode_getfile(const char *name,
 				const struct file_operations *fops,
 				void *priv, int flags);
+struct file *anon_inode_getfile_secure(const char *name,
+				       const struct file_operations *fops,
+				       void *priv, int flags,
+				       const struct inode *context_inode);
 int anon_inode_getfd(const char *name, const struct file_operations *fops,
 		     void *priv, int flags);
 int anon_inode_getfd_secure(const char *name,