Subject: Re: iptables: ensure number of counters is >0 in do_replace()

From: Florian Westphal <[email-masked]>
Date: Wed, 20 May 2015 01:19:50 +0200

Dave Jones <[email-masked]> wrote:
> After improving setsockopt() coverage in trinity, I started triggering
> vmalloc failures pretty reliably from this code path:
> 
> warn_alloc_failed+0xe9/0x140
> __vmalloc_node_range+0x1be/0x270
> vzalloc+0x4b/0x50
> __do_replace+0x52/0x260 [ip_tables]
> do_ipt_set_ctl+0x15d/0x1d0 [ip_tables]
> nf_setsockopt+0x65/0x90
> ip_setsockopt+0x61/0xa0
> raw_setsockopt+0x16/0x60
> sock_common_setsockopt+0x14/0x20
> SyS_setsockopt+0x71/0xd0
> 
> It turns out we don't validate that the num_counters field in the
> struct we pass in from userspace is initialized.
> 
> Signed-off-by: Dave Jones <[email-masked]>
> 
> diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
> index c69db7fa25ee..12a33d178614 100644
> --- a/net/ipv4/netfilter/ip_tables.c
> +++ b/net/ipv4/netfilter/ip_tables.c
> @@ -1262,6 +1262,9 @@ do_replace(struct net *net, const void __user *user, unsigned int len)
>  	/* overflow check */
>  	if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
>  		return -ENOMEM;
> +	if (tmp.num_counters == 0)
> +		return -EINVAL;
> +

Good catch.  Due to iptables wonderful copy-paste programming model,
this also needs fixing in compat_do_replace, ip6tables, arbtables and
ebtables (8 different places, ick).