[syzbot] [netfilter?] KCSAN: data-race in hash_ip4_add / hash_ip4_head

[syzbot] [netfilter?] KCSAN: data-race in hash_ip4_add / hash_ip4_head

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    24f9515de877 Merge tag 'for-linus' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=149f16da580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9
dashboard link: https://syzkaller.appspot.com/bug?extid=1da17e4b41d795df059e
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1bb1f4a7b1f6/disk-24f9515d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6d7e15112efa/vmlinux-24f9515d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ffad41df862f/bzImage-24f9515d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1da17e4b41d795df059e@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in hash_ip4_add / hash_ip4_head

read-write to 0xffff88810e478c19 of 1 bytes by task 6489 on cpu 1:
 hash_ip4_add+0x703/0xf60 net/netfilter/ipset/ip_set_hash_gen.h:965
 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:1751
 ip_set_ad+0x5c0/0x690 net/netfilter/ipset/ip_set_core.c:1841
 ip_set_uadd+0x41/0x50 net/netfilter/ipset/ip_set_core.c:1864
 nfnetlink_rcv_msg+0x509/0x5d0 net/netfilter/nfnetlink.c:302
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2550
 nfnetlink_rcv+0x167/0x1720 net/netfilter/nfnetlink.c:669
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x5c8/0x6f0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x563/0x5b0 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
 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+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810e478c19 of 1 bytes by task 6498 on cpu 0:
 hash_ip4_ext_size net/netfilter/ipset/ip_set_hash_gen.h:823 [inline]
 hash_ip4_head+0x283/0x950 net/netfilter/ipset/ip_set_hash_gen.h:1275
 ip_set_dump_do+0xa34/0xb00 net/netfilter/ipset/ip_set_core.c:1651
 netlink_dump+0x455/0x8a0 net/netlink/af_netlink.c:2325
 netlink_recvmsg+0x420/0x550 net/netlink/af_netlink.c:1976
 sock_recvmsg_nosec net/socket.c:1078 [inline]
 sock_recvmsg+0xf5/0x120 net/socket.c:1100
 ____sys_recvmsg+0xf5/0x280 net/socket.c:2812
 ___sys_recvmsg+0x11f/0x3b0 net/socket.c:2854
 __sys_recvmsg net/socket.c:2887 [inline]
 __do_sys_recvmsg net/socket.c:2893 [inline]
 __se_sys_recvmsg net/socket.c:2890 [inline]
 __x64_sys_recvmsg+0xd1/0x160 net/socket.c:2890
 x64_sys_call+0x2b1a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:48
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x01 -> 0x02

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6498 Comm: syz.4.620 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


---
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