WARNING in l2cap_conn_start

Status: upstream: reported on 2026/03/12 02:14
Subsystems: bluetooth
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+5a3ffe8f0bd0f1dead8e@syzkaller.appspotmail.com
First crash: 145d, last: 3d16h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
43b3980e assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in l2cap_conn_start 2026/06/01 03:47 2026/06/01 03:47 2026/06/01 04:41 6b4a8443

			
		
1a64ac85 assessment-security 💥 WARNING in l2cap_conn_start 2026/05/15 10:19 2026/05/15 10:19 2026/05/15 10:19 9cd3beaa
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/58205a9d03c147c60f...
truncated to first 200 bytes; open job for full error
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [bluetooth?] WARNING in l2cap_conn_start 0 (1) 2026/03/12 02:14

Sample crash report:
------------[ cut here ]------------
workqueue: cannot queue hci_tx_work on wq hci0
WARNING: kernel/workqueue.c:2306 at __queue_work+0xd4a/0x10a0 kernel/workqueue.c:2305, CPU#0: kworker/0:1/10
Modules linked in:
CPU: 0 UID: 0 PID: 10 Comm: kworker/0:1 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+0xd66/0x10a0 kernel/workqueue.c:2305
Code: 49 81 c7 70 01 00 00 4c 8d 35 d6 00 cd 0e 48 89 f8 48 c1 e8 03 80 3c 18 00 74 05 e8 a4 6c a8 00 49 8b 75 18 4c 89 f7 4c 89 fa <67> 48 0f b9 3a 4c 89 e8 48 c1 e8 03 80 3c 18 00 74 08 4c 89 ef e8
RSP: 0018:ffffc9000023f830 EFLAGS: 00010046
RAX: 1ffff1100240098a RBX: dffffc0000000000 RCX: ffff88801bf0a540
RDX: ffff88803fe92970 RSI: ffffffff8ac51380 RDI: ffffffff905aeb30
RBP: 0000000000000020 R08: ffff888012004c3f R09: 1ffff11002400987
R10: dffffc0000000000 R11: ffffed1002400988 R12: 0000000000000008
R13: ffff888012004c38 R14: ffffffff905aeb30 R15: ffff88803fe92970
FS:  0000000000000000(0000) GS:ffff88808c53f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7e31351fb3 CR3: 0000000043827000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2452
 l2cap_conn_start+0x5e2/0xf70 net/bluetooth/l2cap_core.c:1604
 l2cap_info_timeout+0x68/0xa0 net/bluetooth/l2cap_core.c:1714
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0xa8e/0x14e0 kernel/workqueue.c:3405
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3486
 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:	49 81 c7 70 01 00 00 	add    $0x170,%r15
   7:	4c 8d 35 d6 00 cd 0e 	lea    0xecd00d6(%rip),%r14        # 0xecd00e4
   e:	48 89 f8             	mov    %rdi,%rax
  11:	48 c1 e8 03          	shr    $0x3,%rax
  15:	80 3c 18 00          	cmpb   $0x0,(%rax,%rbx,1)
  19:	74 05                	je     0x20
  1b:	e8 a4 6c a8 00       	call   0xa86cc4
  20:	49 8b 75 18          	mov    0x18(%r13),%rsi
  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:	4c 89 e8             	mov    %r13,%rax
  32:	48 c1 e8 03          	shr    $0x3,%rax
  36:	80 3c 18 00          	cmpb   $0x0,(%rax,%rbx,1)
  3a:	74 08                	je     0x44
  3c:	4c 89 ef             	mov    %r13,%rdi
  3f:	e8                   	.byte 0xe8

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/01 06:27 upstream a2cf4ef33184 e611ffe1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in l2cap_conn_start
2026/05/17 10:11 upstream 6916d5703ddf de5aae85 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in l2cap_conn_start
2026/04/27 23:14 upstream 254f49634ee1 ce741359 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in l2cap_conn_start
2026/04/24 05:02 upstream dd6c438c3e64 9cfb3ca7 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in l2cap_conn_start
2026/03/25 03:57 upstream 24f9515de877 35e4ff71 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in l2cap_conn_start
2026/03/12 01:53 upstream b29fb8829bff 2d88ab01 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in l2cap_conn_start
* Struck through repros no longer work on HEAD.