KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (9)

Status: moderation: reported on 2026/10/10 03:00
Subsystems: wireguard
Labels: race:benign prio:high
[Documentation on labels]
Reported-by: syzbot+54fe9e7dbf4babbaeea3@syzkaller.appspotmail.com
First crash: 4d12h, last: 4d12h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
03c9b8ed assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ✅ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (9) 2026/10/08 01:17 2026/10/08 01:17 2026/10/08 01:58 f8f239cf
1659d710 assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (9) 2026/10/06 02:55 2026/10/06 02:55 2026/10/06 03:59 1995e6c7
▶ ▼ Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (8) race:benign prio:high wireguard 6 1 65d 64d 0/29 closed as invalid on 2026/09/11 15:24
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup wireguard 6 1 2126d 2126d 0/29 auto-closed as invalid on 2021/01/17 16:47
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (5) wireguard 6 3 615d 663d 0/29 auto-obsoleted due to no activity on 2025/03/30 05:54
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (7) wireguard 6 3 237d 277d 0/29 auto-obsoleted due to no activity on 2026/04/12 10:27
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (4) wireguard 6 8 720d 834d 0/29 auto-obsoleted due to no activity on 2024/11/23 16:43
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (3) wireguard 6 2 934d 952d 0/29 auto-obsoleted due to no activity on 2024/04/24 09:43
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (6) wireguard 6 3 400d 454d 0/29 auto-obsoleted due to no activity on 2025/10/30 17:16
upstream KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (2) wireguard 6 1 1743d 1743d 0/29 auto-closed as invalid on 2022/02/04 17:58

Sample crash report:
==================================================================
BUG: KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup

write to 0xffff88811a74a13c of 4 bytes by task 29632 on cpu 0:
 wg_index_hashtable_insert+0xdb/0x2a0 drivers/net/wireguard/peerlookup.c:132
 wg_noise_handshake_create_response+0x652/0x700 drivers/net/wireguard/noise.c:713
 wg_packet_send_handshake_response+0x6d/0x120 drivers/net/wireguard/send.c:94
 wg_receive_handshake_packet drivers/net/wireguard/receive.c:154 [inline]
 wg_packet_handshake_receive_worker+0x37d/0x570 drivers/net/wireguard/receive.c:213
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3479
 worker_thread+0x569/0x750 kernel/workqueue.c:3560
 kthread+0x223/0x270 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 0xffff88811a74a13c of 4 bytes by task 30503 on cpu 1:
 wg_index_hashtable_lookup+0x5c/0x120 drivers/net/wireguard/peerlookup.c:211
 wg_noise_handshake_consume_response+0x128/0x8f0 drivers/net/wireguard/noise.c:747
 wg_receive_handshake_packet drivers/net/wireguard/receive.c:166 [inline]
 wg_packet_handshake_receive_worker+0x38b/0x570 drivers/net/wireguard/receive.c:213
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3479
 worker_thread+0x569/0x750 kernel/workqueue.c:3560
 kthread+0x223/0x270 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

value changed: 0xbc95250b -> 0xcf7df5ff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 30503 Comm: kworker/1:6 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Workqueue: wg-kex-wg1 wg_packet_handshake_receive_worker
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/06 02:55 upstream 67f0943b394d f7710056 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup
* Struck through repros no longer work on HEAD.