[moderation] [kernel?] KCSAN: data-race in hash_ip4_add / hash_ip4_gc_do

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fc46aed51f62 Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=104a4aea580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=a5878dead7af0dcd187c
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
CC: [b...@alien8.de dave....@linux.intel.com h...@zytor.com linux-...@vger.kernel.org mi...@redhat.com tg...@kernel.org x...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8ed86af9d76a/disk-fc46aed5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1ab202a433ed/vmlinux-fc46aed5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ef82531838fe/bzImage-fc46aed5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a5878d...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in hash_ip4_add / hash_ip4_gc_do

read-write to 0xffff8881277293b8 of 4 bytes by task 282 on cpu 0:
hash_ip4_gc_do+0x24f/0x5d0 net/netfilter/ipset/ip_set_hash_gen.h:525
hash_ip4_gc+0x12a/0x290 net/netfilter/ipset/ip_set_hash_gen.h:592
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
worker_thread+0x569/0x750 kernel/workqueue.c:3486
kthread+0x221/0x270 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881277293b8 of 4 bytes by task 8810 on cpu 1:
hash_ip4_add+0x238/0xf70 net/netfilter/ipset/ip_set_hash_gen.h:897
hash_ip4_uadt+0x452/0x500 net/netfilter/ipset/ip_set_hash_ip.c:160
call_ad+0x231/0x640 net/netfilter/ipset/ip_set_core.c:1758
ip_set_ad+0x5b1/0x680 net/netfilter/ipset/ip_set_core.c:1848
ip_set_uadd+0x41/0x50 net/netfilter/ipset/ip_set_core.c:1871
nfnetlink_rcv_msg+0x4e2/0x5b0 net/netfilter/nfnetlink.c:300
netlink_rcv_skb+0x11e/0x220 net/netlink/af_netlink.c:2556
nfnetlink_rcv+0x15f/0x1740 net/netfilter/nfnetlink.c:667
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x5a7/0x680 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x5be/0x6f0 net/netlink/af_netlink.c:1900
sock_sendmsg_nosec net/socket.c:775 [inline]
__sock_sendmsg net/socket.c:790 [inline]
____sys_sendmsg+0x532/0x580 net/socket.c:2684
___sys_sendmsg+0x195/0x1e0 net/socket.c:2738
__sys_sendmsg net/socket.c:2770 [inline]
__do_sys_sendmsg net/socket.c:2775 [inline]
__se_sys_sendmsg net/socket.c:2773 [inline]
__x64_sys_sendmsg+0xd4/0x160 net/socket.c:2773
x64_sys_call+0x194c/0x3020 arch/x86/include/generated/asm/syscalls_64.h:47
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000012 -> 0x0000000f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 8810 Comm: syz.2.1239 Tainted: G W syzkaller #0 PREEMPT(lazy)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup