FAILED: patch "[PATCH] scsi: bsg: Report synchronous data copyback failures" failed to apply to 5.10-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.10-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>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x a52f2ad45726d788755b525adcf51f65a6b836ff
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109202554-failed-5.10-a52f2ad45726@kernel.org' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From a52f2ad45726d788755b525adcf51f65a6b836ff Mon Sep 17 00:00:00 2001
From: Yingjie Wang <x-professor@outlook.com>
Date: Fri, 23 Oct 2026 16:23:04 +0000
Subject: [PATCH] scsi: bsg: Report synchronous data copyback failures

scsi_bsg_sg_io_fn() ignores the result of blk_rq_unmap_user(). For a
data-in command that uses a bounce buffer, unmapping copies the completed
data to userspace. If that copy fails, SG_IO can report success despite the
copyback failure.

Capture the unmap status. Preserve an earlier sense-buffer copy error and
otherwise return the data copyback error. This matches the error precedence
used by scsi_complete_sghdr_rq().

On x86_64, a virtio-scsi INQUIRY with an unaligned PROT_NONE destination
made ioctl() return 0 in 20/20 runs before this change and return -1 with
errno EFAULT in 20/20 runs afterward. Writable controls succeeded in 20/20
runs on both kernels.

Fixes: 10e8855b9451 ("bsg: add SG_IO to SG v4")
Cc: stable@vger.kernel.org
Signed-off-by: Yingjie Wang <x-professor@outlook.com>
Reviewed-by: Yang Xiuwei <yangxiuwei@kylinos.cn>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://patch.msgid.link/2561d633cc8cef513d75eb1df260046a4971e783.1792772194.git.x-professor@outlook.com
Signed-off-by: Martin K. Petersen (Oracle) <mkp@kernel.org>
---
 drivers/scsi/scsi_bsg.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/scsi_bsg.c b/drivers/scsi/scsi_bsg.c
index 5eec248a77a6b..37393a8dedd84 100644
--- a/drivers/scsi/scsi_bsg.c
+++ b/drivers/scsi/scsi_bsg.c
@@ -199,7 +199,7 @@ static int scsi_bsg_sg_io_fn(struct request_queue *q, struct sg_io_v4 *hdr,
 	struct scsi_cmnd *scmd;
 	struct request *rq;
 	struct bio *bio;
-	int ret;
+	int ret, unmap_ret;
 
 	if (hdr->protocol != BSG_PROTOCOL_SCSI  ||
 	    hdr->subprotocol != BSG_SUB_PROTOCOL_SCSI_CMD)
@@ -273,7 +273,9 @@ static int scsi_bsg_sg_io_fn(struct request_queue *q, struct sg_io_v4 *hdr,
 	else
 		hdr->dout_resid = scmd->resid_len;
 
-	blk_rq_unmap_user(bio);
+	unmap_ret = blk_rq_unmap_user(bio);
+	if (!ret)
+		ret = unmap_ret;
 
 out_put_request:
 	blk_mq_free_request(rq);
-- 
2.53.0