syzbot


general protection fault in task_work_cancel

Status: upstream: reported on 2026/03/07 05:17
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+741e2278ef71fef03a10@syzkaller.appspotmail.com
First crash: 4d10h, last: 4h04m
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [kernel?] general protection fault in task_work_cancel 0 (1) 2026/03/07 05:17

Sample crash report:
Oops: general protection fault, probably for non-canonical address 0xdffffc000000013c: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000009e0-0x00000000000009e7]
CPU: 0 UID: 0 PID: 30445 Comm: syz.0.6287 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:task_work_pending include/linux/task_work.h:26 [inline]
RIP: 0010:task_work_cancel_match kernel/task_work.c:124 [inline]
RIP: 0010:task_work_cancel+0x8a/0x220 kernel/task_work.c:187
Code: b8 f1 f1 f1 f1 f8 f3 f3 f3 4b 89 44 25 00 e8 ad b9 35 00 43 c6 44 25 04 00 49 89 de 48 81 c3 e0 09 00 00 49 89 df 49 c1 ef 03 <43> 80 3c 27 00 74 08 48 89 df e8 c7 fc 9f 00 48 83 3b 00 75 51 e8
RSP: 0018:ffffc900001f7b20 EFLAGS: 00010206
RAX: ffffffff818fdfc3 RBX: 00000000000009e0 RCX: ffff88802e3a9e80
RDX: 0000000000000003 RSI: ffff88801dfcbf80 RDI: 0000000000000000
RBP: ffffc900001f7bd0 R08: 0000000000000da7 R09: 0000000000400000
R10: 000000000001b4e8 R11: fffff5200003ef93 R12: dffffc0000000000
R13: 1ffff9200003ef68 R14: 0000000000000000 R15: 000000000000013c
FS:  00007f7880fac6c0(0000) GS:ffff888125461000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000039e030 CR3: 0000000095f7e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 cancel_tsync_works security/landlock/tsync.c:415 [inline]
 landlock_restrict_sibling_threads+0xdc4/0x11f0 security/landlock/tsync.c:533
 __do_sys_landlock_restrict_self security/landlock/syscalls.c:574 [inline]
 __se_sys_landlock_restrict_self+0x540/0x810 security/landlock/syscalls.c:482
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7882d9c799
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:00007f7880fac028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007f7883016180 RCX: 00007f7882d9c799
RDX: 0000000000000000 RSI: 000000000000000c RDI: 0000000000000008
RBP: 00007f7882e32bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7883016218 R14: 00007f7883016180 R15: 00007f788313fa48
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:task_work_pending include/linux/task_work.h:26 [inline]
RIP: 0010:task_work_cancel_match kernel/task_work.c:124 [inline]
RIP: 0010:task_work_cancel+0x8a/0x220 kernel/task_work.c:187
Code: b8 f1 f1 f1 f1 f8 f3 f3 f3 4b 89 44 25 00 e8 ad b9 35 00 43 c6 44 25 04 00 49 89 de 48 81 c3 e0 09 00 00 49 89 df 49 c1 ef 03 <43> 80 3c 27 00 74 08 48 89 df e8 c7 fc 9f 00 48 83 3b 00 75 51 e8
RSP: 0018:ffffc900001f7b20 EFLAGS: 00010206

RAX: ffffffff818fdfc3 RBX: 00000000000009e0 RCX: ffff88802e3a9e80
RDX: 0000000000000003 RSI: ffff88801dfcbf80 RDI: 0000000000000000
RBP: ffffc900001f7bd0 R08: 0000000000000da7 R09: 0000000000400000
R10: 000000000001b4e8 R11: fffff5200003ef93 R12: dffffc0000000000
R13: 1ffff9200003ef68 R14: 0000000000000000 R15: 000000000000013c
FS:  00007f7880fac6c0(0000) GS:ffff888125461000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffa64a0b6b0 CR3: 0000000095f7e000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	b8 f1 f1 f1 f1       	mov    $0xf1f1f1f1,%eax
   5:	f8                   	clc
   6:	f3 f3 f3 4b 89 44 25 	repz repz xrelease mov %rax,0x0(%r13,%r12,1)
   d:	00
   e:	e8 ad b9 35 00       	call   0x35b9c0
  13:	43 c6 44 25 04 00    	movb   $0x0,0x4(%r13,%r12,1)
  19:	49 89 de             	mov    %rbx,%r14
  1c:	48 81 c3 e0 09 00 00 	add    $0x9e0,%rbx
  23:	49 89 df             	mov    %rbx,%r15
  26:	49 c1 ef 03          	shr    $0x3,%r15
* 2a:	43 80 3c 27 00       	cmpb   $0x0,(%r15,%r12,1) <-- trapping instruction
  2f:	74 08                	je     0x39
  31:	48 89 df             	mov    %rbx,%rdi
  34:	e8 c7 fc 9f 00       	call   0x9ffd00
  39:	48 83 3b 00          	cmpq   $0x0,(%rbx)
  3d:	75 51                	jne    0x90
  3f:	e8                   	.byte 0xe8

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/07 10:20 upstream 651690480a96 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce general protection fault in task_work_cancel
2026/03/07 08:16 upstream 651690480a96 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce general protection fault in task_work_cancel
2026/03/03 03:28 upstream af4e9ef3d784 28b83e23 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root general protection fault in task_work_cancel
* Struck through repros no longer work on HEAD.