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.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.