CVE-2022-49911: netfilter: ipset: enforce documented limit to prevent allocating huge memory

In the Linux kernel, the following vulnerability has been resolved:

netfilter: ipset: enforce documented limit to prevent allocating huge memory

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.ALLPERMIT hash:net,iface hashsize 1048576 timeout 0 $ for i in $(seq 0 100); do /sbin/ipset add ACL.IN.ALLPERMIT 0.0.0.0/0,kaf$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] dumpstacklvl+0x48/0x60 [Tue Oct 25 00:13:08 2022] warnalloc+0x155/0x180 [Tue Oct 25 00:13:08 2022] vmallocnoderange+0x72a/0x760 [Tue Oct 25 00:13:08 2022] ? hashnetiface4add+0x7c0/0xb20 [Tue Oct 25 00:13:08 2022] ? kmalloclargenode+0x4a/0x90 [Tue Oct 25 00:13:08 2022] kvmallocnode+0xa6/0xd0 [Tue Oct 25 00:13:08 2022] ? hashnetiface4resize+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.