mm: create security context for memfd_secret inodes

Create a security context for the inodes created by memfd_secret(2) via
the LSM hook inode_init_security_anon to allow a fine grained control.
As secret memory areas can affect hibernation and have a global shared
limit access control might be desirable.

Signed-off-by: Christian Göttsche <cgzones@googlemail.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

mm/secretmem.c

@@ -180,11 +180,20 @@ static struct file *secretmem_file_create(unsigned long flags)
 {
 	struct file *file = ERR_PTR(-ENOMEM);
 	struct inode *inode;
+	const char *anon_name = "[secretmem]";
+	const struct qstr qname = QSTR_INIT(anon_name, strlen(anon_name));
+	int err;
 
 	inode = alloc_anon_inode(secretmem_mnt->mnt_sb);
 	if (IS_ERR(inode))
 		return ERR_CAST(inode);
 
+	err = security_inode_init_security_anon(inode, &qname, NULL);
+	if (err) {
+		file = ERR_PTR(err);
+		goto err_free_inode;
+	}
+
 	file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
 				 O_RDWR, &secretmem_fops);
 	if (IS_ERR(file))