syzbot


KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head

Status: moderation: reported on 2026/02/18 04:23
Subsystems: netfilter
[Documentation on labels]
Reported-by: syzbot+5658eefe2ab947b470fd@syzkaller.appspotmail.com
First crash: 51d, last: 47d
✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision Error
1a75b007-c79a-46a7-bd6e-f455de07642b repro KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head 2026/03/08 13:13 2026/03/08 13:13 2026/03/08 13:21 31e9c887f7dc24e04b3ca70d0d54fc34141844b0
c28e45af-8a57-4a36-b391-f78296db093b assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head 2026/02/25 00:04 2026/02/25 00:04 2026/02/25 00:13 305c0ec5cd886e2d13738e28e1b2df9b0ec20fc9
fbae2553-ce37-4044-be80-efbd997ce6fd assessment-kcsan 💥 KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head 2026/01/19 10:38 2026/01/19 10:38 2026/01/19 10:43 a9d6a79219801d2130df3b1a792c57f0e5428e9f LLM did not call tool to set outputs

Sample crash report:
==================================================================
BUG: KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head

read-write to 0xffff888136071719 of 1 bytes by task 17467 on cpu 1:
 hash_ipportip4_add+0x7e1/0x10a0 net/netfilter/ipset/ip_set_hash_gen.h:965
 hash_ipportip4_uadt+0x789/0x8b0 net/netfilter/ipset/ip_set_hash_ipportip.c:195
 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+0x145/0x170 net/socket.c:742
 ____sys_sendmsg+0x31e/0x4a0 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+0x17ba/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888136071719 of 1 bytes by task 17470 on cpu 0:
 hash_ipportip4_ext_size net/netfilter/ipset/ip_set_hash_gen.h:823 [inline]
 hash_ipportip4_head+0x28f/0x790 net/netfilter/ipset/ip_set_hash_gen.h:1276
 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+0x139/0x160 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+0x2cbf/0x3000 arch/x86/include/generated/asm/syscalls_64.h:48
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 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: 17470 Comm: syz.6.3953 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/23 05:57 upstream c072629f05d7 82c9c083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head
2026/01/20 13:28 upstream 24d479d26b25 06648d9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head
2026/01/20 06:52 upstream 24d479d26b25 572effc1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head
2026/01/19 10:38 upstream 24d479d26b25 a9fc5226 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in hash_ipportip4_add / hash_ipportip4_head
* Struck through repros no longer work on HEAD.