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KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer (7)

Status: moderation: reported on 2026/01/05 13:27
Subsystems: wireguard
[Documentation on labels]
Reported-by: syzbot+97539721cdda2fb6da93@syzkaller.appspotmail.com
First crash: 60d, last: 41d
Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer (3) wireguard 6 6 526d 585d 0/29 auto-obsoleted due to no activity on 2024/09/08 23:48
upstream KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer wireguard 6 1 872d 868d 0/29 auto-obsoleted due to no activity on 2023/09/29 08:20
upstream KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer (2) wireguard 6 1 770d 766d 0/29 auto-obsoleted due to no activity on 2024/01/08 19:50
upstream KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer (6) wireguard 6 3 125d 207d 0/29 auto-obsoleted due to no activity on 2025/11/04 23:24
upstream KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer (5) wireguard 6 3 310d 340d 0/29 auto-obsoleted due to no activity on 2025/05/03 20:15
upstream KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer (4) wireguard 6 3 435d 481d 0/29 auto-obsoleted due to no activity on 2024/12/29 16:46

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

read-write to 0xffff88811af56a58 of 8 bytes by task 167 on cpu 1:
 wg_socket_send_skb_to_peer+0xe8/0x130 drivers/net/wireguard/socket.c:183
 wg_socket_send_buffer_to_peer+0xf1/0x120 drivers/net/wireguard/socket.c:200
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0x10d/0x160 drivers/net/wireguard/send.c:51
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x13f/0x270 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read-write to 0xffff88811af56a58 of 8 bytes by task 3503 on cpu 0:
 wg_socket_send_skb_to_peer+0xe8/0x130 drivers/net/wireguard/socket.c:183
 wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline]
 wg_packet_tx_worker+0x12d/0x330 drivers/net/wireguard/send.c:276
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x13f/0x270 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x000000000000005c -> 0x00000000000000f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3503 Comm: kworker/0:9 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: wg-crypt-wg2 wg_packet_tx_worker
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/02 23:00 upstream 4a26e7032d7d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer
2025/11/30 20:30 upstream e69c7c175115 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer
2025/11/14 08:12 upstream 6da43bbeb691 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in wg_socket_send_skb_to_peer / wg_socket_send_skb_to_peer
* Struck through repros no longer work on HEAD.