FAILED: patch "[PATCH] vhost-scsi: zero misaligned I/O bounce pages" failed to apply to 6.6-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.6-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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 01c3a5fa6d641c93c7cef4fb25c5f12938316e18
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109201252-failed-6.6-01c3a5fa6d64@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Thanks,
Sasha

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

From 01c3a5fa6d641c93c7cef4fb25c5f12938316e18 Mon Sep 17 00:00:00 2001
From: Shubham Antil <shubham@octane.security>
Date: Tue, 20 Oct 2026 16:25:03 +0530
Subject: [PATCH] vhost-scsi: zero misaligned I/O bounce pages

The misaligned I/O fallback copies the full bounce scatterlist to the
request buffer during completion.  If a data-in command transfers less
than requested, part of a newly allocated bounce page can remain unwritten.

Allocate bounce pages with __GFP_ZERO so all bytes copied during completion
have a defined value.  This path is already the slow fallback for
misaligned I/O, so the added initialization cost is acceptable.

Found during an LLM-assisted source audit and validated with a QEMU/KVM
vhost-scsi target using misaligned data-in commands.

Fixes: 5ced58bfa132 ("vhost-scsi: Fix alignment handling with windows")
Cc: stable@vger.kernel.org
Assisted-by: LLM (OpenAI Codex, gpt-5.6-sol)
Signed-off-by: Shubham Antil <shubham@octane.security>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20261020105503.75904-1-shubham@octane.security>
---
 drivers/vhost/scsi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 1a0b75cc4cefe..8b166bf5ae773 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -944,7 +944,12 @@ vhost_scsi_copy_iov_to_sgl(struct vhost_scsi_cmd *cmd, struct iov_iter *iter,
 	}
 
 	for_each_sgtable_sg(sg_table, sg, i) {
-		page = alloc_page(GFP_KERNEL);
+		/*
+		 * Completion copies the full bounce buffer, including bytes the
+		 * target did not write. This is already the slow fallback for
+		 * misaligned I/O, so zeroing is acceptable here.
+		 */
+		page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 		if (!page) {
 			ret = -ENOMEM;
 			goto err;
-- 
2.53.0