6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josef Bacik Commit 8444de681a179e41a4eb92d5bbe770a0677074a6 upstream. Commit 41b70df5b38b ("io_uring/net: commit partial buffers on retry") commits ring provided buffers when a receive is going to be retried after a partial transfer, so that another request using the same buffer group can't be handed the memory the first one keeps receiving into. It commits the number of bytes received so far. That does the job for a single buffer which is consumed as a whole, but the request hangs on to all it has mapped: - For a buffer ring with IOU_PBUF_RING_INC only these bytes are consumed. The rest of the buffer stays at the head of the ring. - For a bundle only the buffers which hold these bytes are consumed, the others that were peeked stay in the ring. In both cases the next receive with that buffer group gets memory that the retried request is still going to write to, and whoever comes last overwrites the data of the other. What the retry fills isn't committed at all, as the buffer list isn't known any more at that point. So the kernel hands it out again later on, while the CQE tells the application that it was used, and for an incremental buffer that it is done with. The remainder can't be committed in advance: if the request ends up receiving less, there is no way to tell the application that more was consumed than the CQE accounts for. Complete the request with what it has got instead of retrying it. MSG_WAITALL is no longer honoured for receives into incremental buffers or multi buffer bundles, they can return a short count, with the request marked as failed like for other short MSG_WAITALL transfers. Fixes: 41b70df5b38b ("io_uring/net: commit partial buffers on retry") Assisted-by: LLM Signed-off-by: Josef Bacik Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-40-c1556f5d7bf5@toxicpanda.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- io_uring/net.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) --- a/io_uring/net.c +++ b/io_uring/net.c @@ -500,6 +500,24 @@ static int io_bundle_nbufs(struct io_asy return nbufs; } +/* + * A receive that is retried after a partial transfer keeps writing to what it + * has mapped. io_net_kbuf_recyle() only commits what was filled so far, which + * takes a buffer out of circulation if it's a single one that is consumed as a + * whole. The tail of an incrementally consumed buffer, or the yet unused + * buffers of a bundle, would be up for grabs. They can't be committed in + * advance either, the CQE has no way to tell if they end up not being used. + */ +static bool io_net_kbuf_can_retry(struct io_kiocb *req, + struct io_buffer_list *bl, + struct io_async_msghdr *kmsg) +{ + /* not ring provided, or committed at selection time */ + if (!(req->flags & REQ_F_BUFFERS_COMMIT)) + return true; + return !(bl->flags & IOBL_INC) && iter_is_ubuf(&kmsg->msg.msg_iter); +} + static int io_net_kbuf_recyle(struct io_kiocb *req, struct io_buffer_list *bl, struct io_async_msghdr *kmsg, int len) { @@ -1086,7 +1104,8 @@ retry_multishot: return IOU_ISSUE_SKIP_COMPLETE; return -EAGAIN; } - if (ret > 0 && io_net_retry(sock, flags)) { + if (ret > 0 && io_net_retry(sock, flags) && + io_net_kbuf_can_retry(req, sel.buf_list, kmsg)) { sr->done_io += ret; return io_net_kbuf_recyle(req, sel.buf_list, kmsg, ret); } @@ -1233,7 +1252,8 @@ retry_multishot: return IOU_ISSUE_SKIP_COMPLETE; return -EAGAIN; } - if (ret > 0 && io_net_retry(sock, flags)) { + if (ret > 0 && io_net_retry(sock, flags) && + io_net_kbuf_can_retry(req, sel.buf_list, kmsg)) { sr->len -= ret; sr->buf += ret; sr->done_io += ret;