KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (8)

Status: closed as invalid on 2026/09/11 15:24
Subsystems: wireguard
Labels: race:benign prio:high
[Documentation on labels]
First crash: 48d, last: 48d
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
1de361e8 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ✅ PeripheralTrigger: ❌ RemoteTrigger: ✅ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ✅ VMHostTrigger: ✅ KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (8) 2026/08/08 20:29 2026/08/08 20:29 2026/08/08 20:49 5d63f80b
cdee30cc assessment-kcsan Benign: ✅ KCSAN: data-race in wg_index_hashtable_insert / wg_index_hashtable_lookup (8) 2026/08/08 18:52 2026/08/08 18:52 2026/08/08 19:13 5d63f80b
Similar bugs (7)
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 wireguard 6 1 2110d 2110d 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 598d 646d 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 220d 260d 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 704d 817d 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 917d 935d 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 384d 438d 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 1726d 1726d 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 0xffff88812d05077c of 4 bytes by task 3375 on cpu 1:
 wg_index_hashtable_insert+0xda/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: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 0xffff88812d05077c of 4 bytes by task 3410 on cpu 0:
 wg_index_hashtable_lookup+0x5b/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: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

value changed: 0xabf9bbc1 -> 0x33c4f176

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3410 Comm: kworker/0:4 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: wg-kex-wg2 wg_packet_handshake_receive_worker
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/05 23:21 upstream 0d8395707651 cd5b1963 .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.