syzbot


KCSAN: data-race in nci_rsp_packet / skb_queue_purge_reason

Status: moderation: reported on 2026/01/08 13:00
Subsystems: net nfc
[Documentation on labels]
Reported-by: syzbot+921ca345cb60eead10e4@syzkaller.appspotmail.com
First crash: 64d, last: 64d

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

write to 0xffff888109ca5918 of 8 bytes by task 12752 on cpu 1:
 __skb_queue_head_init include/linux/skbuff.h:2290 [inline]
 skb_queue_splice_init include/linux/skbuff.h:2376 [inline]
 skb_queue_purge_reason+0x121/0x250 net/core/skbuff.c:3946
 skb_queue_purge include/linux/skbuff.h:3438 [inline]
 nci_open_device net/nfc/nci/core.c:541 [inline]
 nci_dev_up+0x33f/0x8f0 net/nfc/nci/core.c:632
 nfc_dev_up+0x103/0x1b0 net/nfc/core.c:118
 nfc_genl_dev_up+0x53/0x90 net/nfc/netlink.c:775
 genl_family_rcv_msg_doit+0x143/0x1b0 net/netlink/genetlink.c:1115
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0x422/0x460 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2552
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x145/0x180 net/socket.c:742
 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2630
 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2684
 __sys_sendmsg net/socket.c:2716 [inline]
 __do_sys_sendmsg net/socket.c:2721 [inline]
 __se_sys_sendmsg net/socket.c:2719 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2719
 x64_sys_call+0x191e/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888109ca5918 of 8 bytes by task 12012 on cpu 0:
 skb_queue_empty include/linux/skbuff.h:1926 [inline]
 nci_rsp_packet+0xddf/0xe30 net/nfc/nci/rsp.c:426
 nci_rx_work+0x16f/0x2c0 net/nfc/nci/core.c:1551
 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+0x122/0x1b0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0xffff88811907e000 -> 0xffff888109ca5918

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 12012 Comm: kworker/u8:56 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: nfc2_nci_rx_wq nci_rx_work
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/09 23:09 upstream 439fc29dfd3b 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in nci_rsp_packet / skb_queue_purge_reason
* Struck through repros no longer work on HEAD.