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>
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 634e676..f9aeb40 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1287,8 +1287,10 @@
 
 	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;
 }