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

[Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx>]

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.

Reported-by: Daniel Xu <dxu@xxxxxxxxx>
Signed-off-by: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxx>
---
 net/netfilter/ipset/ip_set_hash_gen.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

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);
-- 
2.30.2