Re: [PATCH v1] vdpa: Complement vdpa_nl_policy for nlattr length check

Michael S. Tsirkin
2023-07-23T09:22:57Z

On Sun, Jul 23, 2023 at 04:05:07PM +0800, Lin Ma wrote:
> The vdpa_nl_policy structure is used to validate the nlattr when parsing
> the incoming nlmsg. It will ensure the attribute being described produces
> a valid nlattr pointer in info->attrs before entering into each handler
> in vdpa_nl_ops.
>
> That is to say, the missing part in vdpa_nl_policy may lead to illegal
> nlattr after parsing, which could lead to OOB read just like CVE-2023-3773.

Hmm.

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-3773

** RESERVED ** This candidate has been reserved by an organization or individual that will use it when announcing a new security problem. When the candidate has been publicized, the details for this candidate will be provided.

> This patch adds three missing nla_policy to avoid such bugs.
>
> Fixes: 90fea5a800c3 ("vdpa: device feature provisioning")
> Fixes: 13b00b135665 ("vdpa: Add support for querying vendor statistics")
> Fixes: ad69dd0bf26b ("vdpa: Introduce query of device config layout")
> Signed-off-by: Lin Ma <linma@zju.edu.cn>

I don't know how OOB triggers but this duplication is problematic I
think: we are likely to forget again in the future. Isn't there a way
to block everything that is not listed?

> ---
> drivers/vdpa/vdpa.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 965e32529eb8..f2f654fd84e5 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -1247,8 +1247,11 @@ static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
> [VDPA_ATTR_MGMTDEV_DEV_NAME] = { .type = NLA_STRING },
> [VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
> [VDPA_ATTR_DEV_NET_CFG_MACADDR] = NLA_POLICY_ETH_ADDR,
> + [VDPA_ATTR_DEV_NET_CFG_MAX_VQP] = { .type = NLA_U16 },
> /* virtio spec 1.1 section 5.1.4.1 for valid MTU range */
> [VDPA_ATTR_DEV_NET_CFG_MTU] = NLA_POLICY_MIN(NLA_U16, 68),
> + [VDPA_ATTR_DEV_QUEUE_INDEX] = { .type = NLA_U32 },
> + [VDPA_ATTR_DEV_FEATURES] = { .type = NLA_U64 },
> };
>
> static const struct genl_ops vdpa_nl_ops[] = {
> --
> 2.17.1