KASAN: use-after-free Read in l2cap_unregister_user

Status: upstream: reported C repro on 2024/11/07 17:33
Reported-by: syzbot+51b9f0aeb761754e57b8@syzkaller.appspotmail.com
First crash: 676d, last: 6d23h
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/08/03 upstream (ToT) 075b74841bd0 C Failed due to an error; will retry later
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: use-after-free Read in l2cap_unregister_user origin:upstream 19 syz, C error 123 31d 663d 0/3 upstream: reported C repro on 2024/11/20 17:00
upstream KASAN: slab-use-after-free Read in l2cap_unregister_user bluetooth 22 syz, C done 46133 130d 682d 29/29 fixed on 2026/05/21 07:50
linux-6.6 KASAN: slab-use-after-free Read in l2cap_unregister_user origin:upstream missing-backport 19 syz error 90 109d 452d 0/2 upstream: reported syz repro on 2025/06/19 23:39
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2026/08/24 07:53 2h54m bisect fix linux-6.1.y OK (0) job log log
2026/07/19 19:11 3h09m bisect fix linux-6.1.y OK (0) job log log
2026/06/18 03:22 2h48m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
Unable to handle kernel paging request at virtual address dfff800000000000
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
Mem abort info:
  ESR = 0x0000000096000006
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000006
  CM = 0, WnR = 0
[dfff800000000000] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4686 Comm: syz.3.47 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : l2cap_unregister_user+0x34/0x194 net/bluetooth/l2cap_core.c:1775
lr : l2cap_unregister_user+0x30/0x194 net/bluetooth/l2cap_core.c:1774
sp : ffff800021be77b0
x29: ffff800021be77b0 x28: ffff0000dad39c00 x27: 00000000000089f0
x26: dfff800000000000 x25: dfff800000000000 x24: ffff800021be7840
x23: 1ffff0000437cf2b x22: dfff800000000000 x21: 0000000000000000
x20: 0000000000000000 x19: ffff0000d9f38090 x18: 1fffe00033e7217e
x17: ffff80001539d000 x16: ffff8000082dd25c x15: ffff00019f390bfc
x14: 0000000000000001 x13: 1fffe00033e74870 x12: 0000000000000000
x11: ff00800010df18bc x10: 0000000000000000 x9 : ffff800010df18bc
x8 : 0000000000000000 x7 : ffff80000825ab48 x6 : 0000000000000000
x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff800021be73c0 x1 : ffff0000d9f38090 x0 : 0000000000000000
Call trace:
 l2cap_unregister_user+0x34/0x194 net/bluetooth/l2cap_core.c:1775
 hidp_connection_del+0xb4/0x154 net/bluetooth/hidp/core.c:1441
 do_hidp_sock_ioctl net/bluetooth/hidp/sock.c:97 [inline]
 hidp_sock_ioctl+0x60c/0xa70 net/bluetooth/hidp/sock.c:128
 sock_do_ioctl+0x100/0x258 net/socket.c:1202
 sock_ioctl+0x234/0x828 net/socket.c:1321
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: aa0003f4 f2fbfff6 97c80048 d343fe88 (38766908) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	aa0003f4 	mov	x20, x0
   4:	f2fbfff6 	movk	x22, #0xdfff, lsl #48
   8:	97c80048 	bl	0xffffffffff200128
   c:	d343fe88 	lsr	x8, x20, #3
* 10:	38766908 	ldrb	w8, [x8, x22] <-- trapping instruction

Crashes (166):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/08 05:01 linux-6.1.y cf82dcca9634 680aa3e1 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in l2cap_unregister_user
2026/04/19 02:03 linux-6.1.y 7c87defbd336 303e2802 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in l2cap_unregister_user
2026/01/07 16:54 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/01/01 05:58 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/24 09:45 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/23 11:33 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/20 12:44 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/16 05:32 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/10 16:10 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/09 09:59 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/09 06:03 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/05 03:25 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/04 17:37 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/02 09:02 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/26 23:44 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/05 09:10 linux-6.1.y f6e38ae624cf a6c9c731 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/03/10 04:05 linux-6.1.y f2ddafa93a25 6972f302 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/03/09 15:49 linux-6.1.y f2ddafa93a25 176bead5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/03/01 04:36 linux-6.1.y 779f9571ac3e 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/02/25 13:34 linux-6.1.y 779f9571ac3e 94a9671e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/02/11 17:56 linux-6.1.y 8ce36b2849ef 75707236 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/22 13:20 linux-6.1.y cd9b81672742 a16aed1d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/19 07:41 linux-6.1.y cd9b81672742 20d37d28 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/16 17:11 linux-6.1.y bec0e10ee67e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/08 14:25 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/06 16:08 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/04 19:41 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/03 15:01 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/01/03 02:30 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/30 08:41 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/23 17:44 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/23 00:49 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/19 11:32 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/18 11:55 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/14 18:28 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/08 03:33 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/02 23:41 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/12/01 01:01 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/11/29 23:19 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/11/27 22:16 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/11/24 08:44 linux-6.1.y f6e38ae624cf 4fb8ef37 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/11/13 17:49 linux-6.1.y f6e38ae624cf 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/11/12 05:10 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_unregister_user
2025/11/07 13:01 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_unregister_user
2025/11/05 20:59 linux-6.1.y f6e38ae624cf a6c9c731 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2024/11/07 17:32 linux-6.1.y 7c15117f9468 867e44df .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/09/08 03:54 linux-6.1.y cf82dcca9634 680aa3e1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in l2cap_unregister_user
2026/05/18 07:38 linux-6.1.y c27210688955 de5aae85 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in l2cap_unregister_user
2026/04/19 01:16 linux-6.1.y 7c87defbd336 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 BUG: unable to handle kernel paging request in l2cap_unregister_user
* Struck through repros no longer work on HEAD.