linux-kernel - [PATCH AUTOSEL 5.15 13/16] vdpa: clean up get_config

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Date:   Sat, 22 Jan 2022 19:12:12 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Laura Abbott <labbott@...nel.org>,
        Luo Likang <luolikang@...ocus.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Sasha Levin <sashal@...nel.org>, jasowang@...hat.com,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 13/16] vdpa: clean up get_config_size ret value handling

From: Laura Abbott <labbott@...nel.org>

[ Upstream commit 870aaff92e959e29d40f9cfdb5ed06ba2fc2dae0 ]

The return type of get_config_size is size_t so it makes
sense to change the type of the variable holding its result.

That said, this already got taken care of (differently, and arguably
not as well) by commit 3ed21c1451a1 ("vdpa: check that offsets are
within bounds").

The added 'c->off > size' test in that commit will be done as an
unsigned comparison on 32-bit (safe due to not being signed).

On a 64-bit platform, it will be done as a signed comparison, but in
that case the comparison will be done in 64-bit, and 'c->off' being an
u32 it will be valid thanks to the extended range (ie both values will
be positive in 64 bits).

So this was a real bug, but it was already addressed and marked for stable.

Signed-off-by: Laura Abbott <labbott@...nel.org>
Reported-by: Luo Likang <luolikang@...ocus.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/vhost/vdpa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index d62f05d056b7b..913cd465f9f1e 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -195,7 +195,7 @@ static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
 				      struct vhost_vdpa_config *c)
 {
 	struct vdpa_device *vdpa = v->vdpa;
-	long size = vdpa->config->get_config_size(vdpa);
+	size_t size = vdpa->config->get_config_size(vdpa);

 	if (c->len == 0 || c->off > size)
 		return -EINVAL;
-- 
2.34.1