KASAN: use-after-free Read in l2cap_unregister_user

Status: upstream: reported C repro on 2024/11/20 17:00
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+e903ad7f4bd1974ccf75@syzkaller.appspotmail.com
First crash: 639d, last: 8d11h
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2025/09/28 upstream (ToT) 51a24b7deaae C [report] KASAN: slab-use-after-free Read in l2cap_unregister_user
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: use-after-free Read in l2cap_unregister_user 19 syz, C 164 33d 652d 0/3 upstream: reported C repro on 2024/11/07 17:33
upstream KASAN: slab-use-after-free Read in l2cap_unregister_user bluetooth 22 syz, C done 46133 107d 658d 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 85d 428d 0/2 upstream: reported syz repro on 2025/06/19 23:39
▶ ▼ Last patch testing requests (6)
Created Duration User Patch Repo Result
2026/08/14 04:22 16m retest repro linux-5.15.y report job log log
2026/07/31 02:04 1h00m retest repro linux-5.15.y no crash log
2026/06/02 21:40 15m retest repro linux-5.15.y report log
2026/03/12 12:07 11m retest repro linux-5.15.y report log
2026/01/01 11:00 13m retest repro linux-5.15.y report log
2025/10/12 05:59 18m retest repro linux-5.15.y report log

Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 PID: 4663 Comm: syz.4.100 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:l2cap_unregister_user+0x27/0x1a0 net/bluetooth/l2cap_core.c:1869
Code: 1f 40 00 55 41 57 41 56 41 55 41 54 53 50 48 89 f3 49 89 fe 49 bd 00 00 00 00 00 fc ff df e8 60 a0 95 f8 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 1a bf da f8 41 bf 58 09 00 00 4d
RSP: 0018:ffffc90003bf79b0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88802bd40090 RCX: ffff888021fd9dc0
RDX: 0000000000000000 RSI: ffff88802bd40090 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88807c2b9deb R09: 1ffff1100f8573bd
R10: dffffc0000000000 R11: ffffed100f8573be R12: 1ffff9200077ef6b
R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007f7d45cd26c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7d466df540 CR3: 00000000731d9000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 hidp_connection_del+0xac/0x160 net/bluetooth/hidp/core.c:1422
 do_hidp_sock_ioctl net/bluetooth/hidp/sock.c:96 [inline]
 hidp_sock_ioctl+0x3a7/0x610 net/bluetooth/hidp/sock.c:127
 sock_do_ioctl+0xfb/0x320 net/socket.c:1147
 sock_ioctl+0x4d2/0x710 net/socket.c:1266
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f7d46691e59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7d45cd2028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f7d4690b090 RCX: 00007f7d46691e59
RDX: 0000200000000000 RSI: 00000000400448c9 RDI: 0000000000000004
RBP: 00007f7d46727d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7d4690b128 R14: 00007f7d4690b090 R15: 00007fff09377118
 </TASK>
Modules linked in:
---[ end trace 2ba0965e6c899a9b ]---
RIP: 0010:l2cap_unregister_user+0x27/0x1a0 net/bluetooth/l2cap_core.c:1869
Code: 1f 40 00 55 41 57 41 56 41 55 41 54 53 50 48 89 f3 49 89 fe 49 bd 00 00 00 00 00 fc ff df e8 60 a0 95 f8 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 1a bf da f8 41 bf 58 09 00 00 4d
RSP: 0018:ffffc90003bf79b0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88802bd40090 RCX: ffff888021fd9dc0
RDX: 0000000000000000 RSI: ffff88802bd40090 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88807c2b9deb R09: 1ffff1100f8573bd
R10: dffffc0000000000 R11: ffffed100f8573be R12: 1ffff9200077ef6b
R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007f7d45cd26c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff3b25c4ff8 CR3: 00000000731d9000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 1 bytes skipped:
   0:	40 00 55 41          	rex add %dl,0x41(%rbp)
   4:	57                   	push   %rdi
   5:	41 56                	push   %r14
   7:	41 55                	push   %r13
   9:	41 54                	push   %r12
   b:	53                   	push   %rbx
   c:	50                   	push   %rax
   d:	48 89 f3             	mov    %rsi,%rbx
  10:	49 89 fe             	mov    %rdi,%r14
  13:	49 bd 00 00 00 00 00 	movabs $0xdffffc0000000000,%r13
  1a:	fc ff df
  1d:	e8 60 a0 95 f8       	call   0xf895a082
  22:	4c 89 f0             	mov    %r14,%rax
  25:	48 c1 e8 03          	shr    $0x3,%rax
* 29:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	4c 89 f7             	mov    %r14,%rdi
  33:	e8 1a bf da f8       	call   0xf8dabf52
  38:	41 bf 58 09 00 00    	mov    $0x958,%r15d
  3e:	4d                   	rex.WRB

Crashes (123):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/18 06:34 linux-5.15.y 93741761e5e3 de5aae85 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in l2cap_unregister_user
2026/04/16 17:15 linux-5.15.y 91d48252ad4b 4743f87d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/04/08 05:47 linux-5.15.y 91d48252ad4b 2c961e87 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/03/29 09:57 linux-5.15.y 91d48252ad4b b5ceaad2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/02/19 20:21 linux-5.15.y 3330a8d33e08 c8d8c52d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/02/15 12:23 linux-5.15.y e45d5d41c134 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/02/12 17:15 linux-5.15.y e45d5d41c134 504cb1bf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/02/12 02:46 linux-5.15.y e45d5d41c134 76a109e2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/02/02 01:01 linux-5.15.y 9eec9a14ee10 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/01/15 09:44 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2026/01/03 02:40 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/18 05:25 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/17 18:25 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/14 02:27 linux-5.15.y 68efe5a6c16a d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/05 00:42 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/12/02 12:45 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/29 04:44 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/28 22:56 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/26 22:40 linux-5.15.y cc5ec8769306 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/24 22:57 linux-5.15.y cc5ec8769306 bf6fe8fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/13 22:04 linux-5.15.y cc5ec8769306 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/11/12 00:09 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/10/31 04:51 linux-5.15.y cc5ec8769306 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/10/28 16:04 linux-5.15.y ac56c046adf4 fd2207e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/10/22 00:57 linux-5.15.y ac56c046adf4 9832ed61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/10/19 04:30 linux-5.15.y 29e53a5b1c4f 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/09/27 21:27 linux-5.15.y 43bb85222e53 001c9061 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/09/26 16:53 linux-5.15.y 43bb85222e53 0abd0691 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/09/26 11:34 linux-5.15.y 43bb85222e53 0abd0691 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/09/09 05:27 linux-5.15.y 7a6c2d093c45 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/08/26 22:09 linux-5.15.y c79648372d02 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/30 23:16 linux-5.15.y c79648372d02 f8f2b4da .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/22 19:16 linux-5.15.y c79648372d02 8e9d1dc1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/18 23:14 linux-5.15.y c79648372d02 7117feec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/09 02:03 linux-5.15.y 3dea0e7f549e 4d9fdfa4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/06 09:47 linux-5.15.y 3dea0e7f549e 4f67c4ae .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/04 19:55 linux-5.15.y 3dea0e7f549e d869b261 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/02 06:03 linux-5.15.y 3dea0e7f549e bc80e4f0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2024/11/20 16:59 linux-5.15.y 0a51d2d4527b 4fca1650 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in l2cap_unregister_user
2025/07/25 02:01 linux-5.15.y c79648372d02 fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/07/24 21:23 linux-5.15.y c79648372d02 65d60d73 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/07/16 04:42 linux-5.15.y 89950c454265 03fcfc4b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/07/11 15:21 linux-5.15.y 2f693b607545 3cda49cf .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/07/04 02:17 linux-5.15.y 3dea0e7f549e 76ad128c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2025/07/02 16:06 linux-5.15.y 3dea0e7f549e bc80e4f0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-arm64 KASAN: use-after-free Read in l2cap_unregister_user
2026/05/18 05:14 linux-5.15.y 93741761e5e3 de5aae85 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in l2cap_unregister_user
* Struck through repros no longer work on HEAD.