Hi Pablo, I'm following up with our hallway chat yesterday about how ipset hash:net,iface can easily OOM. Here's a quick reproducer (stolen from https://bugzilla.kernel.org/show_bug.cgi?id=199107): $ 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 This used to cause a NULL ptr deref panic before https://github.com/torvalds/linux/commit/2b33d6ffa9e38f344418976b06 . Now it'll either allocate a huge amount of memory or fail a vmalloc(): [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 <...> Note that this behavior is somewhat documented (https://ipset.netfilter.org/ipset.man.html): > 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. I'm not sure how hard it would be to enforce a limit, but I think it would be a bit better to error than allocate many GBs of memory. Thanks, Daniel
