[syzbot] [bluetooth?] WARNING in l2cap_send_conn_req

syzbot
2026-05-06T08:54:36Z

Hello,

syzbot found the following issue on:

HEAD commit: f1a5e78a55eb Merge tag 'drm-fixes-2026-05-02' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=117699ba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7f195f6be48c12ec
dashboard link: https://syzkaller.appspot.com/bug?extid=97721dd81f792e838ba0
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-f1a5e78a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c76a260376ef/vmlinux-f1a5e78a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/31edd841d28f/bzImage-f1a5e78a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+97721dd81f792e838ba0@syzkaller.appspotmail.com

------------[ cut here ]------------
workqueue: cannot queue hci_tx_work on wq hci0
WARNING: kernel/workqueue.c:2298 at __queue_work+0xd1f/0xfc0 kernel/workqueue.c:2296, CPU#0: kworker/0:5/5309
Modules linked in:
CPU: 0 UID: 0 PID: 5309 Comm: kworker/0:5 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events l2cap_info_timeout
RIP: 0010:__queue_work+0xd4a/0xfc0 kernel/workqueue.c:2296
Code: 83 c5 18 4c 89 e8 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 ef e8 47 54 a5 00 49 8b 75 00 49 81 c7 70 01 00 00 4c 89 f7 4c 89 fa <67> 48 0f b9 3a 48 83 c4 58 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc
RSP: 0018:ffffc9000e42f778 EFLAGS: 00010082
RAX: 1ffff1100254618a RBX: 0000000000000008 RCX: ffff88800e470000
RDX: ffff888043643970 RSI: ffffffff8a9d8360 RDI: ffffffff9033c3b0
RBP: 0000000000000020 R08: ffff888012a30c3f R09: 1ffff11002546187
R10: dffffc0000000000 R11: ffffed1002546188 R12: dffffc0000000000
R13: ffff888012a30c50 R14: ffffffff9033c3b0 R15: ffff888043643970
FS: 0000000000000000(0000) GS:ffff88808c885000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fba154bda50 CR3: 0000000012441000 CR4: 0000000000352ef0
Call Trace:
<TASK>
queue_work_on+0x106/0x1d0 kernel/workqueue.c:2432
l2cap_send_conn_req+0x243/0x370 net/bluetooth/l2cap_core.c:1253
l2cap_start_connection net/bluetooth/l2cap_core.c:1408 [inline]
l2cap_conn_start+0xb2b/0xf20 net/bluetooth/l2cap_core.c:1549
l2cap_info_timeout+0x68/0xa0 net/bluetooth/l2cap_core.c:1685
process_one_work kernel/workqueue.c:3302 [inline]
process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
----------------
Code disassembly (best guess):
0: 83 c5 18 add $0x18,%ebp
3: 4c 89 e8 mov %r13,%rax
6: 48 c1 e8 03 shr $0x3,%rax
a: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
f: 74 08 je 0x19
11: 4c 89 ef mov %r13,%rdi
14: e8 47 54 a5 00 call 0xa55460
19: 49 8b 75 00 mov 0x0(%r13),%rsi
1d: 49 81 c7 70 01 00 00 add $0x170,%r15
24: 4c 89 f7 mov %r14,%rdi
27: 4c 89 fa mov %r15,%rdx
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: 48 83 c4 58 add $0x58,%rsp
33: 5b pop %rbx
34: 41 5c pop %r12
36: 41 5d pop %r13
38: 41 5e pop %r14
3a: 41 5f pop %r15
3c: 5d pop %rbp
3d: c3 ret
3e: cc int3
3f: cc int3

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