Merge tag 'io_uring-6.3-2023-04-06' of git://git.kernel.dk/linux

Pull io_uring fixes from Jens Axboe:
 "Just two minor fixes for provided buffers - one where we could
  potentially leak a buffer, and one where the returned values was
  off-by-one in some cases"

* tag 'io_uring-6.3-2023-04-06' of git://git.kernel.dk/linux:
  io_uring: fix memory leak when removing provided buffers
  io_uring: fix return value when removing provided buffers

Author: torvalds

io_uring/io_uring.c

@@ -2789,8 +2789,8 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	io_eventfd_unregister(ctx);
 	io_alloc_cache_free(&ctx->apoll_cache, io_apoll_cache_free);
 	io_alloc_cache_free(&ctx->netmsg_cache, io_netmsg_cache_free);
-	mutex_unlock(&ctx->uring_lock);
 	io_destroy_buffers(ctx);
+	mutex_unlock(&ctx->uring_lock);
 	if (ctx->sq_creds)
 		put_cred(ctx->sq_creds);
 	if (ctx->submitter_task)

io_uring/kbuf.c

@@ -228,17 +228,18 @@ static int __io_remove_buffers(struct io_ring_ctx *ctx,
 		return i;
 	}
 
-	/* the head kbuf is the list itself */
+	/* protects io_buffers_cache */
+	lockdep_assert_held(&ctx->uring_lock);
+
 	while (!list_empty(&bl->buf_list)) {
 		struct io_buffer *nxt;
 
 		nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
-		list_del(&nxt->list);
+		list_move(&nxt->list, &ctx->io_buffers_cache);
 		if (++i == nbufs)
 			return i;
 		cond_resched();
 	}
-	i++;
 
 	return i;
 }