syzbot


KASAN: wild-memory-access Read in l2cap_connect_cfm

Status: upstream: reported on 2025/10/02 10:15
Reported-by: syzbot+ed4382699fd4eb756532@syzkaller.appspotmail.com
First crash: 187d, last: 8d09h
Similar bugs (6)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in l2cap_connect_cfm bluetooth 19 syz inconclusive 36 397d 476d 0/29 closed as invalid on 2025/03/07 00:26
linux-6.1 KASAN: use-after-free Read in l2cap_connect_cfm 19 6 314d 535d 0/3 auto-obsoleted due to no activity on 2025/09/05 21:35
upstream KASAN: wild-memory-access Read in l2cap_connect_cfm bluetooth 19 C error 284 10m 386d 0/29 upstream: reported C repro on 2025/03/17 15:57
linux-6.6 KASAN: slab-use-after-free Read in l2cap_connect_cfm origin:upstream 19 C 16 14d 201d 0/2 upstream: reported C repro on 2025/09/18 08:10
linux-5.15 KASAN: use-after-free Read in l2cap_connect_cfm (2) origin:lts-only 19 C error 12 6d17h 195d 0/3 upstream: reported C repro on 2025/09/24 14:26
linux-5.15 KASAN: use-after-free Read in l2cap_connect_cfm 19 3 327d 426d 0/3 auto-obsoleted due to no activity on 2025/08/23 07:27

Sample crash report:
kobject_add_internal failed for hci1:201 with -EEXIST, don't try to register things with the same name in the same directory.
Bluetooth: hci1: failed to register connection device
==================================================================
BUG: KASAN: wild-memory-access in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: wild-memory-access in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: wild-memory-access in l2cap_chan_lock include/net/bluetooth/l2cap.h:865 [inline]
BUG: KASAN: wild-memory-access in l2cap_conn_ready net/bluetooth/l2cap_core.c:1785 [inline]
BUG: KASAN: wild-memory-access in l2cap_connect_cfm+0x4f4/0xd98 net/bluetooth/l2cap_core.c:8424
Read of size 4 at addr deacfffffffffc84 by task kworker/u5:0/47

CPU: 0 PID: 47 Comm: kworker/u5:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
Workqueue: hci1 hci_rx_work
Call trace:
 dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_report+0x40/0x68 mm/kasan/report.c:423
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x258/0x290 mm/kasan/generic.c:189
 __kasan_check_read+0x2c/0x3c mm/kasan/shadow.c:31
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 l2cap_chan_lock include/net/bluetooth/l2cap.h:865 [inline]
 l2cap_conn_ready net/bluetooth/l2cap_core.c:1785 [inline]
 l2cap_connect_cfm+0x4f4/0xd98 net/bluetooth/l2cap_core.c:8424
 hci_connect_cfm+0x98/0x130 include/net/bluetooth/hci_core.h:1817
 le_conn_complete_evt+0xd30/0x1244 net/bluetooth/hci_event.c:5882
 hci_le_conn_complete_evt+0x114/0x3f4 net/bluetooth/hci_event.c:5908
 hci_le_meta_evt+0x2c0/0x4a0 net/bluetooth/hci_event.c:7101
 hci_event_func net/bluetooth/hci_event.c:7412 [inline]
 hci_event_packet+0x6b8/0xf18 net/bluetooth/hci_event.c:7467
 hci_rx_work+0x328/0xa84 net/bluetooth/hci_core.c:4109
 process_one_work+0x7f8/0x13a4 kernel/workqueue.c:2292
 worker_thread+0x8c4/0xfec kernel/workqueue.c:2439
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850
==================================================================
Unable to handle kernel paging request at virtual address fbd51fffffffff90
KASAN: maybe wild-memory-access in range [0xdeacfffffffffc80-0xdeacfffffffffc87]
Mem abort info:
  ESR = 0x0000000096000004
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000004
  CM = 0, WnR = 0
[fbd51fffffffff90] address between user and kernel address ranges
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 47 Comm: kworker/u5:0 Tainted: G    B              syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
Workqueue: hci1 hci_rx_work
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : atomic_read include/linux/atomic/atomic-instrumented.h:28 [inline]
pc : l2cap_chan_lock include/net/bluetooth/l2cap.h:865 [inline]
pc : l2cap_conn_ready net/bluetooth/l2cap_core.c:1785 [inline]
pc : l2cap_connect_cfm+0x500/0xd98 net/bluetooth/l2cap_core.c:8424
lr : instrument_atomic_read include/linux/instrumented.h:72 [inline]
lr : atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
lr : l2cap_chan_lock include/net/bluetooth/l2cap.h:865 [inline]
lr : l2cap_conn_ready net/bluetooth/l2cap_core.c:1785 [inline]
lr : l2cap_connect_cfm+0x4f4/0xd98 net/bluetooth/l2cap_core.c:8424
sp : ffff80001cf67600
x29: ffff80001cf67680 x28: dfff800000000000 x27: 1fffe0001e910007
x26: 0000000000000001 x25: 0000000000000080 x24: deacfffffffffc84
x23: ffff0000dacad81a x22: dead000000000100 x21: ffff0000dacada60
x20: ffff0000f4880039 x19: ffff0000dacad800 x18: ffff800011b9bf60
x17: 1fffe00033eaa57e x16: ffff80000804309c x15: ffff80001521d000
x14: 0000000000000001 x13: 1ffff00002fc1b6c x12: 0000000000100000
x11: 000000000002da1d x10: ffff8000326fc000 x9 : 0000000000000007
x8 : 1bd59fffffffff90 x7 : 0000000000000004 x6 : ffff800008257984
x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff800008193d18
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
 atomic_read include/linux/atomic/atomic-instrumented.h:28 [inline]
 l2cap_chan_lock include/net/bluetooth/l2cap.h:865 [inline]
 l2cap_conn_ready net/bluetooth/l2cap_core.c:1785 [inline]
 l2cap_connect_cfm+0x500/0xd98 net/bluetooth/l2cap_core.c:8424
 hci_connect_cfm+0x98/0x130 include/net/bluetooth/hci_core.h:1817
 le_conn_complete_evt+0xd30/0x1244 net/bluetooth/hci_event.c:5882
 hci_le_conn_complete_evt+0x114/0x3f4 net/bluetooth/hci_event.c:5908
 hci_le_meta_evt+0x2c0/0x4a0 net/bluetooth/hci_event.c:7101
 hci_event_func net/bluetooth/hci_event.c:7412 [inline]
 hci_event_packet+0x6b8/0xf18 net/bluetooth/hci_event.c:7467
 hci_rx_work+0x328/0xa84 net/bluetooth/hci_core.c:4109
 process_one_work+0x7f8/0x13a4 kernel/workqueue.c:2292
 worker_thread+0x8c4/0xfec kernel/workqueue.c:2439
 kthread+0x250/0x2d8 kernel/kthread.c:376
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850
Code: 97ccce15 d343ff08 12000b09 11000d29 (38fc6908) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	97ccce15 	bl	0xffffffffff333854
   4:	d343ff08 	lsr	x8, x24, #3
   8:	12000b09 	and	w9, w24, #0x7
   c:	11000d29 	add	w9, w9, #0x3
* 10:	38fc6908 	ldrsb	w8, [x8, x28] <-- trapping instruction

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/30 12:55 linux-6.1.y 1989cd3d56e2 dcaebc52 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: wild-memory-access Read in l2cap_connect_cfm
2025/10/02 10:15 linux-6.1.y 7b34dc04e4ff 267f56c6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: wild-memory-access Read in l2cap_connect_cfm
2026/02/05 14:50 linux-6.1.y cd9b81672742 4936e85c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_connect_cfm
2025/11/07 00:54 linux-6.1.y f6e38ae624cf 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_connect_cfm
* Struck through repros no longer work on HEAD.