Re: FAILED: patch "[PATCH] io_uring: fix off-by one bvec index" failed to apply to 5.4-stable tree

[Jens Axboe <axboe@kernel.dk>]

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On 11/30/23 7:31 AM, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 5.4-stable tree.

And the 5.4 variant attached.

-- 
Jens Axboe


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From aa4df1efa47241f8b9faab93f9d73eda4aa9ccf3 Mon Sep 17 00:00:00 2001
From: Keith Busch <kbusch@kernel.org>
Date: Mon, 20 Nov 2023 14:18:31 -0800
Subject: [PATCH] io_uring: fix off-by one bvec index

commit d6fef34ee4d102be448146f24caf96d7b4a05401 upstream.

If the offset equals the bv_len of the first registered bvec, then the
request does not include any of that first bvec. Skip it so that drivers
don't have to deal with a zero length bvec, which was observed to break
NVMe's PRP list creation.

Cc: stable@vger.kernel.org
Fixes: bd11b3a391e3 ("io_uring: don't use iov_iter_advance() for fixed buffers")
Signed-off-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20231120221831.2646460-1-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3683ddeb625a..adc263400471 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1256,7 +1256,7 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw,
 		 */
 		const struct bio_vec *bvec = imu->bvec;
 
-		if (offset <= bvec->bv_len) {
+		if (offset < bvec->bv_len) {
 			iov_iter_advance(iter, offset);
 		} else {
 			unsigned long seg_skip;
-- 
2.42.0