[moderation] [bluetooth?] KCSAN: data-race in __hci_cmd_sync_sk / hci_cmd_sync_cancel_sync

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cfd4039213e7 Merge tag 'io_uring-6.19-20251208' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=152f9992580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c3201432211be40f
dashboard link: https://syzkaller.appspot.com/bug?extid=f1074c17b4ca5c22ad9d
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [johan....@gmail.com linux-b...@vger.kernel.org linux-...@vger.kernel.org luiz....@gmail.com mar...@holtmann.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9f556ae6e3c4/disk-cfd40392.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/efcf53c1d459/vmlinux-cfd40392.xz
kernel image: https://storage.googleapis.com/syzbot-assets/858f42961336/bzImage-cfd40392.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f1074c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __hci_cmd_sync_sk / hci_cmd_sync_cancel_sync

write to 0xffff88810b33c8f8 of 4 bytes by task 44 on cpu 1:
hci_cmd_sync_cancel_sync+0x67/0xa0 net/bluetooth/hci_sync.c:691
hci_send_cmd_sync net/bluetooth/hci_core.c:4119 [inline]
hci_cmd_work+0x27a/0x320 net/bluetooth/hci_core.c:4152
process_one_work kernel/workqueue.c:3257 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
worker_thread+0x582/0x770 kernel/workqueue.c:3421
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff88810b33c8f8 of 4 bytes by task 5534 on cpu 0:
__hci_cmd_sync_sk+0x34f/0x640 net/bluetooth/hci_sync.c:176
__hci_cmd_sync_status_sk net/bluetooth/hci_sync.c:263 [inline]
__hci_cmd_sync_status net/bluetooth/hci_sync.c:287 [inline]
hci_cmd_sync_status+0x4b/0x100 net/bluetooth/hci_sync.c:298
hci_dev_cmd+0x4e4/0x500 net/bluetooth/hci_core.c:-1
hci_sock_ioctl+0x578/0x7f0 net/bluetooth/hci_sock.c:1157
sock_do_ioctl+0x73/0x220 net/socket.c:1254
sock_ioctl+0x41b/0x610 net/socket.c:1375
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
x64_sys_call+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5534 Comm: syz.2.673 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
Bluetooth: hci0: Opcode 0x0c20 failed: -22


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