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

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Lin Ma <linma@zju.edu.cn>
Cc: xuanzhuo@linux.alibaba.com, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v1] vdpa: Complement vdpa_nl_policy for nlattr length check
Date: Sun, 23 Jul 2023 05:22:03 -0400	[thread overview]
Message-ID: <20230723050656-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20230723080507.3716924-1-linma@zju.edu.cn>

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

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