Re: [PATCH v1] macvlan: add forgotten nla_policy for IFLA_MACVLAN_BC_CUTOFF

[Simon Horman]

+ Herbert Xu

On Sun, Jul 23, 2023 at 04:02:05PM +0800, Lin Ma wrote:
> The previous commit 954d1fa1ac93 ("macvlan: Add netlink attribute for
> broadcast cutoff") added one additional attribute named
> IFLA_MACVLAN_BC_CUTOFF to allow broadcast cutfoff.
> 
> However, it forgot to describe the nla_policy at macvlan_policy
> (drivers/net/macvlan.c). Hence, this suppose NLA_S32 (4 bytes) integer
> can be faked as empty (0 bytes) by a malicious user, which could leads
> to OOB in heap just like CVE-2023-3773.
> 
> To fix it, this commit just completes the nla_policy description for
> IFLA_MACVLAN_BC_CUTOFF. This enforces the length check and avoids the
> potential OOB read.
> 
> Fixes: 954d1fa1ac93 ("macvlan: Add netlink attribute for broadcast cutoff")
> Signed-off-by: Lin Ma <linma@xxxxxxxxxx>

Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>

> ---
>  drivers/net/macvlan.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
> index 4a53debf9d7c..ed908165a8b4 100644
> --- a/drivers/net/macvlan.c
> +++ b/drivers/net/macvlan.c
> @@ -1746,6 +1746,7 @@ static const struct nla_policy macvlan_policy[IFLA_MACVLAN_MAX + 1] = {
>  	[IFLA_MACVLAN_MACADDR_COUNT] = { .type = NLA_U32 },
>  	[IFLA_MACVLAN_BC_QUEUE_LEN] = { .type = NLA_U32 },
>  	[IFLA_MACVLAN_BC_QUEUE_LEN_USED] = { .type = NLA_REJECT },
> +	[IFLA_MACVLAN_BC_CUTOFF] = { .type = NLA_S32 },
>  };
>  
>  int macvlan_link_register(struct rtnl_link_ops *ops)
> -- 
> 2.17.1
> 
>