userfaultfd: add missing mmput() in error path

This fixes a memleak if anon_inode_getfile() fails in userfaultfd().
Signed-off-by: Eric Biggers <ebiggers3@gmail.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/userfaultfd.c

@@ -1287,8 +1287,10 @@ static struct file *userfaultfd_file_create(int flags)
 
 	file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
 				  O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
-	if (IS_ERR(file))
+	if (IS_ERR(file)) {
+		mmput(ctx->mm);
 		kmem_cache_free(userfaultfd_ctx_cachep, ctx);
+	}
 out:
 	return file;
 }