Re: [PATCH v2] netfilter: ipset: enforce documented limit to prevent allocating huge memory

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Nov 02, 2022 at 10:40:47AM +0100, Jozsef Kadlecsik wrote:
> Daniel Xu reported that the hash:net,iface type of the ipset subsystem does
> not limit adding the same network with different interfaces to a set, which
> can lead to huge memory usage or allocation failure.
> 
> The quick reproducer is
> 
> $ ipset create ACL.IN.ALL_PERMIT hash:net,iface hashsize 1048576 timeout 0
> $ for i in $(seq 0 100); do /sbin/ipset add ACL.IN.ALL_PERMIT 0.0.0.0/0,kaf_$i timeout 0 -exist; done
> 
> The backtrace when vmalloc fails:
> 
>         [Tue Oct 25 00:13:08 2022] ipset: vmalloc error: size 1073741848, exceeds total pages
>         <...>
>         [Tue Oct 25 00:13:08 2022] Call Trace:
>         [Tue Oct 25 00:13:08 2022]  <TASK>
>         [Tue Oct 25 00:13:08 2022]  dump_stack_lvl+0x48/0x60
>         [Tue Oct 25 00:13:08 2022]  warn_alloc+0x155/0x180
>         [Tue Oct 25 00:13:08 2022]  __vmalloc_node_range+0x72a/0x760
>         [Tue Oct 25 00:13:08 2022]  ? hash_netiface4_add+0x7c0/0xb20
>         [Tue Oct 25 00:13:08 2022]  ? __kmalloc_large_node+0x4a/0x90
>         [Tue Oct 25 00:13:08 2022]  kvmalloc_node+0xa6/0xd0
>         [Tue Oct 25 00:13:08 2022]  ? hash_netiface4_resize+0x99/0x710
>         <...>
> 
> The fix is to enforce the limit documented in the ipset(8) manpage:
> 
> >  The internal restriction of the hash:net,iface set type is that the same
> >  network prefix cannot be stored with more than 64 different interfaces
> >  in a single set.

Applied, thanks