fuse: missing copy_finish in fuse-over-io-uring argument copies

Fix a possible reference count leak of payload pages during
fuse argument copies.

[Joanne: simplified error cleanup]

Fixes: c090c8abae4b ("fuse: Add io-uring sqe commit and fetch support")
Cc: [e-mail] # v6.14
Signed-off-by: Cheng Ding <[e-mail]>
Signed-off-by: Bernd Schubert <[e-mail]>
Reviewed-by: Joanne Koong <[e-mail]>
Signed-off-by: Miklos Szeredi <[e-mail]>

fs/fuse/dev.c

···
 }
 
 /* Unmap and put previous page of userspace buffer */
-static void fuse_copy_finish(struct fuse_copy_state *cs)
+void fuse_copy_finish(struct fuse_copy_state *cs)
 {
 	if (cs->currbuf) {
 		struct pipe_buffer *buf = cs->currbuf;

fs/fuse/dev_uring.c

···
 	cs.is_uring = true;
 	cs.req = req;
 
-	return fuse_copy_out_args(&cs, args, ring_in_out.payload_sz);
+	err = fuse_copy_out_args(&cs, args, ring_in_out.payload_sz);
+	fuse_copy_finish(&cs);
+	return err;
 }
 
  /*
···
 	/* copy the payload */
 	err = fuse_copy_args(&cs, num_args, args->in_pages,
 			     (struct fuse_arg *)in_args, 0);
+	fuse_copy_finish(&cs);
 	if (err) {
 		pr_info_ratelimited("%s fuse_copy_args failed\n", __func__);
 		return err;

fs/fuse/fuse_dev_i.h

···
 
 void fuse_copy_init(struct fuse_copy_state *cs, bool write,
 			   struct iov_iter *iter);
+void fuse_copy_finish(struct fuse_copy_state *cs);
 int fuse_copy_args(struct fuse_copy_state *cs, unsigned int numargs,
 		   unsigned int argpages, struct fuse_arg *args,
 		   int zeroing);