For placeholder buffers, &dummy_ubuf is assigned which is a static value. When buffers are attempted cloned, don't attempt to grab a reference to it, as we both don't need it and it'll actively fail as dummy_ubuf doesn't have a valid reference count setup. Link: https://lore.kernel.org/io-uring/Zw8dkUzsxQ5LgAJL@ly-workstation/ Reported-by: Lai, Yi <yi1.lai@xxxxxxxxxxxxxxx> Fixes: 7cc2a6eadcd7 ("io_uring: add IORING_REGISTER_COPY_BUFFERS method") Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index 33a3d156a85b..6f3b6de230bd 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -1176,7 +1176,8 @@ static int io_clone_buffers(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx for (i = 0; i < nbufs; i++) { struct io_mapped_ubuf *src = src_ctx->user_bufs[i]; - refcount_inc(&src->refs); + if (src != &dummy_ubuf) + refcount_inc(&src->refs); user_bufs[i] = src; } -- Jens Axboe
