[moderation] [nfc?] [net?] KCSAN: data-race in nci_rsp_packet / skb_queue_purge_reason

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 439fc29dfd3b Merge tag 'drm-fixes-2025-11-09' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11399412580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d2e0bc0ae94545f7
dashboard link: https://syzkaller.appspot.com/bug?extid=921ca345cb60eead10e4
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [da...@davemloft.net edum...@google.com ho...@kernel.org kr...@kernel.org ku...@kernel.org linux-...@vger.kernel.org net...@vger.kernel.org pab...@redhat.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d6deee7d825b/disk-439fc29d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cd66fc6b27ef/vmlinux-439fc29d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4e501bf05228/bzImage-439fc29d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+921ca3...@syzkaller.appspotmail.com

==================================================================
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
==================================================================


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