From 2e10dc9c2a87e2b34a29fa28ba756ab66290def0 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 13 Jun 2025 11:01:49 -0600 Subject: [PATCH] io_uring/kbuf: don't truncate end buffer for multiple buffer peeks commit 26ec15e4b0c1d7b25214d9c0be1d50492e2f006c upstream. If peeking a bunch of buffers, normally io_ring_buffers_peek() will truncate the end buffer. This isn't optimal as presumably more data will be arriving later, and hence it's better to stop with the last full buffer rather than truncate the end buffer. Cc: stable@vger.kernel.org Fixes: 35c8711c8fc4 ("io_uring/kbuf: add helpers for getting/peeking multiple buffers") Reported-by: Christian Mazakas Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- io_uring/kbuf.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 94602d1f7e6f..c9289597522f 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -262,8 +262,11 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg, /* truncate end piece, if needed, for non partial buffers */ if (len > arg->max_len) { len = arg->max_len; - if (!(bl->flags & IOBL_INC)) + if (!(bl->flags & IOBL_INC)) { + if (iov != arg->iovs) + break; buf->len = len; + } } iov->iov_base = u64_to_user_ptr(buf->addr);