[PATCH 6.19 056/220] io_uring/kbuf: fix missing BUF_MORE for incremental buffers at EOF

Greg Kroah-Hartman
2026-03-23T13:52:16Z

From: Jens Axboe <axboe@kernel.dk>

commit 3ecd3e03144b38a21a3b70254f1b9d2e16629b09 upstream.

For a zero length transfer, io_kbuf_inc_commit() is called with !len.
Since we never enter the while loop to consume the buffers,
io_kbuf_inc_commit() ends up returning true, consuming the buffer. But
if no data was consumed, by definition it cannot have consumed the
buffer. Return false for that case.

Reported-by: Martin Michaelis <code@mgjm.de>
Cc: stable@vger.kernel.org
Fixes: ae98dbf43d75 ("io_uring/kbuf: add support for incremental buffer consumption")
Link: https://github.com/axboe/liburing/issues/1553
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
io_uring/kbuf.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -34,6 +34,10 @@ struct io_provide_buf {

static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len)
{
+ /* No data consumed, return false early to avoid consuming the buffer */
+ if (!len)
+ return false;
+
while (len) {
struct io_uring_buf *buf;
u32 buf_len, this_len;