Hi Daniel, On Tue, 25 Oct 2022, Daniel Xu wrote: > 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. That's a bug, actually the limit is not enforced in spite of the documentation. The next patch fixes it and I'm going to submit to Pablo: diff --git a/net/netfilter/ipset/ip_set_hash_gen.h b/net/netfilter/ipset/ip_set_hash_gen.h index 6e391308431d..3f8853ed32e9 100644 --- a/net/netfilter/ipset/ip_set_hash_gen.h +++ b/net/netfilter/ipset/ip_set_hash_gen.h @@ -61,10 +61,6 @@ tune_bucketsize(u8 curr, u32 multi) */ return n > curr && n <= AHASH_MAX_TUNED ? n : curr; } -#define TUNE_BUCKETSIZE(h, multi) \ - ((h)->bucketsize = tune_bucketsize((h)->bucketsize, multi)) -#else -#define TUNE_BUCKETSIZE(h, multi) #endif /* A hash bucket */ @@ -936,7 +932,11 @@ mtype_add(struct ip_set *set, void *value, const struct ip_set_ext *ext, goto set_full; /* Create a new slot */ if (n->pos >= n->size) { - TUNE_BUCKETSIZE(h, multi); +#ifdef IP_SET_HASH_WITH_MULTI + if (h->bucketsize >= AHASH_MAX_TUNED) + goto set_full; + h->bucketsize = tune_bucketsize(h->bucketsize, multi); +#endif if (n->size >= AHASH_MAX(h)) { /* Trigger rehashing */ mtype_data_next(&h->next, d); Best regards, Jozsef - E-mail : kadlec@xxxxxxxxxxxxxxxxx, kadlecsik.jozsef@xxxxxxxxx PGP key : https://wigner.hu/~kadlec/pgp_public_key.txt Address : Wigner Research Centre for Physics H-1525 Budapest 114, POB. 49, Hungary
