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

[Kirill Tkhai]

On 06.01.2019 14:00, Kirill Tkhai wrote:
> 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);

Do we need GFP_HIGHMEM here?

>>  	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;
>>
>