vdpa: clean up get_config_size ret value handling

stable inclusion
from stable-v5.17
commit 870aaff9
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=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 3ed21c14 ("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: NLaura Abbott <labbott@kernel.org>
Reported-by: NLuo Likang <luolikang@nsfocus.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NPengyuan Zhao <zhaopengyuan@hisilicon.com>

drivers/vhost/vdpa.c

@@ -197,7 +197,7 @@ 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;