Re: FAILED: patch "[PATCH] io_uring/kbuf: don't truncate end buffer for bundles" failed to apply to 6.18-stable tree

[Jens Axboe <axboe@kernel.dk>]

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On 6/15/26 8:18 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 6.18-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

Here's one for 6.18-stable.

-- 
Jens Axboe

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From b01e74c189cc3e17fbb98f28f69245b259144429 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Sun, 7 Jun 2026 16:05:47 -0600
Subject: [PATCH 2/2] io_uring/kbuf: don't truncate end buffer for bundles

Commit 70f4886bcbb929e88038c8807f1daf7fc587ae7c upstream.

If buffers have been peeked for a bundle receive, the kernel will
truncate the end buffer, if the available length is shorter than the
buffer itself. This is unnecessary, as applications iterating bundle
receives must always use the minimum size of the buffer length and the
remaining number of bytes in the bundle. The examples in liburing do
that as well, eg examples/proxy.c.

If the kernel does truncate this buffer AND the current transfer fails,
then the buffer will be left with a smaller size than what is otherwise
available.

Just remove the buffer truncation, as it's not necessary in the first
place.

Link: https://lore.kernel.org/io-uring/CAAEr8jbY60noGj1fw_k91UJRBkyiRVoS6=nLhZ7Svwidjn4CAA@mail.gmail.com/
Reported-by: Federico Brasili <federico.brasili@gmail.com>
Cc: stable@vger.kernel.org
Fixes: 35c8711c8fc4 ("io_uring/kbuf: add helpers for getting/peeking multiple buffers")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 io_uring/kbuf.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 32d3b8d26bf0..c260d5f34cf3 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -305,7 +305,6 @@ static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
 				arg->partial_map = 1;
 				if (iov != arg->iovs)
 					break;
-				buf->len = len;
 			}
 		}
 
-- 
2.53.0