ila: serialize calls to nf_register_net_hooks()

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

ila: serialize calls to nf_register_net_hooks()

syzbot found a race in ila_add_mapping() [1]

commit 031ae72825ce ("ila: call nf_unregister_net_hooks() sooner")

attempted to fix a similar issue.

Looking at the syzbot repro, we have concurrent ILA_CMD_ADD commands.

Add a mutex to make sure at most one thread is calling nf_register_net_hooks().

[1]

BUG: KASAN: slab-use-after-free in rht_key_hashfn include/linux/rhashtable.h:159 [inline]

BUG: KASAN: slab-use-after-free in __rhashtable_lookup.constprop.0+0x426/0x550 include/linux/rhashtable.h:604

Read of size 4 at addr ffff888028f40008 by task dhcpcd/5501

CPU: 1 UID: 0 PID: 5501 Comm: dhcpcd Not tainted 6.13.0-rc4-syzkaller-00054-gd6ef8b40d075 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024

Call Trace:

<IRQ>

__dump_stack lib/dump_stack.c:94 [inline]

dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120

print_address_description mm/kasan/report.c:378 [inline]

print_report+0xc3/0x620 mm/kasan/report.c:489

kasan_report+0xd9/0x110 mm/kasan/report.c:602

rht_key_hashfn include/linux/rhashtable.h:159 [inline]

__rhashtable_lookup.constprop.0+0x426/0x550 include/linux/rhashtable.h:604

rhashtable_lookup include/linux/rhashtable.h:646 [inline]

rhashtable_lookup_fast include/linux/rhashtable.h:672 [inline]

ila_lookup_wildcards net/ipv6/ila/ila_xlat.c:127 [inline]

ila_xlat_addr net/ipv6/ila/ila_xlat.c:652 [inline]

ila_nf_input+0x1ee/0x620 net/ipv6/ila/ila_xlat.c:185

nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]

nf_hook_slow+0xbb/0x200 net/netfilter/core.c:626

nf_hook.constprop.0+0x42e/0x750 include/linux/netfilter.h:269

NF_HOOK include/linux/netfilter.h:312 [inline]

ipv6_rcv+0xa4/0x680 net/ipv6/ip6_input.c:309

__netif_receive_skb_one_core+0x12e/0x1e0 net/core/dev.c:5672

__netif_receive_skb+0x1d/0x160 net/core/dev.c:5785

process_backlog+0x443/0x15f0 net/core/dev.c:6117

__napi_poll.constprop.0+0xb7/0x550 net/core/dev.c:6883

napi_poll net/core/dev.c:6952 [inline]

net_rx_action+0xa94/0x1010 net/core/dev.c:7074

handle_softirqs+0x213/0x8f0 kernel/softirq.c:561

__do_softirq kernel/softirq.c:595 [inline]

invoke_softirq kernel/softirq.c:435 [inline]

__irq_exit_rcu+0x109/0x170 kernel/softirq.c:662

irq_exit_rcu+0x9/0x30 kernel/softirq.c:678

instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]

sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1049