[moderation] [bridge?] KCSAN: data-race in br_fdb_update / br_fdb_update (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c8ebd433459b Merge tag 'nfsd-6.19-2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16274afc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=b18e64ebc37dc6ac3638
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [bri...@lists.linux.dev da...@davemloft.net edum...@google.com ho...@kernel.org ido...@nvidia.com ku...@kernel.org linux-...@vger.kernel.org net...@vger.kernel.org pab...@redhat.com ra...@blackwall.org]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d4c0e188b92f/disk-c8ebd433.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/25522cdc5fa6/vmlinux-c8ebd433.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a1499d747012/bzImage-c8ebd433.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b18e64...@syzkaller.appspotmail.com

ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
==================================================================
BUG: KCSAN: data-race in br_fdb_update / br_fdb_update

write to 0xffff8881a9996040 of 8 bytes by interrupt on cpu 0:
br_fdb_update+0x13e/0x460 net/bridge/br_fdb.c:1006
br_handle_frame_finish+0x340/0xfc0 net/bridge/br_input.c:144
br_nf_hook_thresh+0x1eb/0x220 net/bridge/br_netfilter_hooks.c:-1
br_nf_pre_routing_finish_ipv6+0x4d1/0x570 net/bridge/br_netfilter_ipv6.c:-1
NF_HOOK include/linux/netfilter.h:318 [inline]
br_nf_pre_routing_ipv6+0x1fa/0x2b0 net/bridge/br_netfilter_ipv6.c:184
br_nf_pre_routing+0x52b/0xbd0 net/bridge/br_netfilter_hooks.c:508
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
br_handle_frame+0x4f0/0x9e0 net/bridge/br_input.c:442
__netif_receive_skb_core+0x5df/0x1920 net/core/dev.c:6026
__netif_receive_skb_one_core net/core/dev.c:6137 [inline]
__netif_receive_skb+0x59/0x270 net/core/dev.c:6252
process_backlog+0x228/0x420 net/core/dev.c:6604
__napi_poll+0x5f/0x300 net/core/dev.c:7668
napi_poll net/core/dev.c:7731 [inline]
net_rx_action+0x425/0x8c0 net/core/dev.c:7883
handle_softirqs+0xba/0x290 kernel/softirq.c:622
do_softirq+0x45/0x60 kernel/softirq.c:523
__local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450
local_bh_enable include/linux/bottom_half.h:33 [inline]
update_defense_level+0x589/0x5c0 net/netfilter/ipvs/ip_vs_ctl.c:209
defense_work_handler+0x1f/0x80 net/netfilter/ipvs/ip_vs_ctl.c:234
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
worker_thread+0x582/0x770 kernel/workqueue.c:3421
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff8881a9996040 of 8 bytes by interrupt on cpu 1:
br_fdb_update+0x106/0x460 net/bridge/br_fdb.c:1005
br_handle_frame_finish+0x340/0xfc0 net/bridge/br_input.c:144
br_nf_hook_thresh+0x1eb/0x220 net/bridge/br_netfilter_hooks.c:-1
br_nf_pre_routing_finish_ipv6+0x4d1/0x570 net/bridge/br_netfilter_ipv6.c:-1
NF_HOOK include/linux/netfilter.h:318 [inline]
br_nf_pre_routing_ipv6+0x1fa/0x2b0 net/bridge/br_netfilter_ipv6.c:184
br_nf_pre_routing+0x52b/0xbd0 net/bridge/br_netfilter_hooks.c:508
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
br_handle_frame+0x4f0/0x9e0 net/bridge/br_input.c:442
__netif_receive_skb_core+0x5df/0x1920 net/core/dev.c:6026
__netif_receive_skb_one_core net/core/dev.c:6137 [inline]
__netif_receive_skb+0x59/0x270 net/core/dev.c:6252
process_backlog+0x228/0x420 net/core/dev.c:6604
__napi_poll+0x5f/0x300 net/core/dev.c:7668
napi_poll net/core/dev.c:7731 [inline]
net_rx_action+0x425/0x8c0 net/core/dev.c:7883
handle_softirqs+0xba/0x290 kernel/softirq.c:622
do_softirq+0x45/0x60 kernel/softirq.c:523
__local_bh_enable_ip+0x70/0x80 kernel/softirq.c:450
local_bh_enable include/linux/bottom_half.h:33 [inline]
fpregs_unlock arch/x86/include/asm/fpu/api.h:77 [inline]
kernel_fpu_end+0x6c/0x80 arch/x86/kernel/fpu/core.c:480
blake2s_compress+0x67/0x1740 lib/crypto/x86/blake2s.h:42
blake2s_update+0xa3/0x160 lib/crypto/blake2s.c:119
hmac+0x141/0x270 drivers/net/wireguard/noise.c:324
kdf+0x10b/0x1d0 drivers/net/wireguard/noise.c:375
mix_dh drivers/net/wireguard/noise.c:413 [inline]
wg_noise_handshake_create_initiation+0x1ac/0x520 drivers/net/wireguard/noise.c:550
wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:34 [inline]
wg_packet_handshake_send_worker+0xb2/0x160 drivers/net/wireguard/send.c:51
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
worker_thread+0x582/0x770 kernel/workqueue.c:3421
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x000000010000112f -> 0x0000000100001130

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 15770 Comm: kworker/u8:34 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: wg-kex-wg0 wg_packet_handshake_send_worker
==================================================================
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
net_ratelimit: 56413 callbacks suppressed
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!
ICMPv6: NA: aa:aa:aa:aa:aa:1c advertised our address fe80::aa on veth1_to_bridge!


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[Aleksandr Nogikh]

#syz upstream

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