linux-kernel - [PATCH AUTOSEL 6.6 1/8] virtio_blk: fix snprintf truncation compiler warning

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Date: Mon,  8 Jan 2024 07:27:17 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Stefan Hajnoczi <stefanha@...hat.com>,
	Suwan Kim <suwan.kim027@...il.com>,
	kernel test robot <lkp@...el.com>,
	"Michael S . Tsirkin" <mst@...hat.com>,
	Sasha Levin <sashal@...nel.org>,
	jasowang@...hat.com,
	axboe@...nel.dk,
	virtualization@...ts.linux.dev,
	linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 1/8] virtio_blk: fix snprintf truncation compiler warning

From: Stefan Hajnoczi <stefanha@...hat.com>

[ Upstream commit b8e0792449928943c15d1af9f63816911d139267 ]

Commit 4e0400525691 ("virtio-blk: support polling I/O") triggers the
following gcc 13 W=1 warnings:

drivers/block/virtio_blk.c: In function ‘init_vq’:
drivers/block/virtio_blk.c:1077:68: warning: ‘%d’ directive output may be truncated writing between 1 and 11 bytes into a region of size 7 [-Wformat-truncation=]
 1077 |                 snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i);
      |                                                                    ^~
drivers/block/virtio_blk.c:1077:58: note: directive argument in the range [-2147483648, 65534]
 1077 |                 snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i);
      |                                                          ^~~~~~~~~~~~~
drivers/block/virtio_blk.c:1077:17: note: ‘snprintf’ output between 11 and 21 bytes into a destination of size 16
 1077 |                 snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is a false positive because the lower bound -2147483648 is
incorrect. The true range of i is [0, num_vqs - 1] where 0 < num_vqs <
65536.

The code mixes int, unsigned short, and unsigned int types in addition
to using "%d" for an unsigned value. Use unsigned short and "%u"
consistently to solve the compiler warning.

Cc: Suwan Kim <suwan.kim027@...il.com>
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202312041509.DIyvEt9h-lkp@intel.com/
Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
Message-Id: <20231204140743.1487843-1-stefanha@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/block/virtio_blk.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 4a4b9bad551e8..225c86c74d4e9 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1021,12 +1021,12 @@ static void virtblk_config_changed(struct virtio_device *vdev)
 static int init_vq(struct virtio_blk *vblk)
 {
 	int err;
-	int i;
+	unsigned short i;
 	vq_callback_t **callbacks;
 	const char **names;
 	struct virtqueue **vqs;
 	unsigned short num_vqs;
-	unsigned int num_poll_vqs;
+	unsigned short num_poll_vqs;
 	struct virtio_device *vdev = vblk->vdev;
 	struct irq_affinity desc = { 0, };
 
@@ -1070,13 +1070,13 @@ static int init_vq(struct virtio_blk *vblk)
 
 	for (i = 0; i < num_vqs - num_poll_vqs; i++) {
 		callbacks[i] = virtblk_done;
-		snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%d", i);
+		snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req.%u", i);
 		names[i] = vblk->vqs[i].name;
 	}
 
 	for (; i < num_vqs; i++) {
 		callbacks[i] = NULL;
-		snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%d", i);
+		snprintf(vblk->vqs[i].name, VQ_NAME_LEN, "req_poll.%u", i);
 		names[i] = vblk->vqs[i].name;
 	}
 
-- 
2.43.0