Re: [PATCH v2] netfilter: account ebt_table_info to kmemcg

[Kirill Tkhai]

On 03.01.2019 06:14, Shakeel Butt wrote:
> The [ip,ip6,arp]_tables use x_tables_info internally and the underlying
> memory is already accounted to kmemcg. Do the same for ebtables. The
> syzbot, by using setsockopt(EBT_SO_SET_ENTRIES), was able to OOM the
> whole system from a restricted memcg, a potential DoS.
> 
> By accounting the ebt_table_info, the memory used for ebt_table_info can
> be contained within the memcg of the allocating process. However the
> lifetime of ebt_table_info is independent of the allocating process and
> is tied to the network namespace. So, the oom-killer will not be able to
> relieve the memory pressure due to ebt_table_info memory. The memory for
> ebt_table_info is allocated through vmalloc. Currently vmalloc does not
> handle the oom-killed allocating process correctly and one large
> allocation can bypass memcg limit enforcement. So, with this patch,
> at least the small allocations will be contained. For large allocations,
> we need to fix vmalloc.
> 
> Reported-by: syzbot+7713f3aa67be76b1552c@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
> Cc: Florian Westphal <fw@xxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
> Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> Cc: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>
> Cc: Roopa Prabhu <roopa@xxxxxxxxxxxxxxxxxxx>
> Cc: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Linux MM <linux-mm@xxxxxxxxx>
> Cc: netfilter-devel@xxxxxxxxxxxxxxx
> Cc: coreteam@xxxxxxxxxxxxx
> Cc: bridge@xxxxxxxxxxxxxxxxxxxxxxxxxx
> Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>
> ---
> Changelog since v1:
> - More descriptive commit message.

Reviewed-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>

> 
>  net/bridge/netfilter/ebtables.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
> index 491828713e0b..5e55cef0cec3 100644
> --- a/net/bridge/netfilter/ebtables.c
> +++ b/net/bridge/netfilter/ebtables.c
> @@ -1137,14 +1137,16 @@ static int do_replace(struct net *net, const void __user *user,
>  	tmp.name[sizeof(tmp.name) - 1] = 0;
>  
>  	countersize = COUNTER_OFFSET(tmp.nentries) * nr_cpu_ids;
> -	newinfo = vmalloc(sizeof(*newinfo) + countersize);
> +	newinfo = __vmalloc(sizeof(*newinfo) + countersize, GFP_KERNEL_ACCOUNT,
> +			    PAGE_KERNEL);
>  	if (!newinfo)
>  		return -ENOMEM;
>  
>  	if (countersize)
>  		memset(newinfo->counters, 0, countersize);
>  
> -	newinfo->entries = vmalloc(tmp.entries_size);
> +	newinfo->entries = __vmalloc(tmp.entries_size, GFP_KERNEL_ACCOUNT,
> +				     PAGE_KERNEL);
>  	if (!newinfo->entries) {
>  		ret = -ENOMEM;
>  		goto free_newinfo;
>