syzbot


general protection fault in task_work_cancel_match

Status: moderation: reported on 2026/02/20 04:47
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+911d99dc200feac03ea6@syzkaller.appspotmail.com
Fix commit: 929553bbb4cd landlock: Fully release unused TSYNC work entries
Patched on: [ci-qemu-gce-upstream-auto ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce], missing on: [ci-qemu-native-arm64-kvm ci-qemu2-riscv64 ci-upstream-gce-arm64 ci2-upstream-usb]
First crash: 57d, last: 24d
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
49b58f3a-ee65-4e73-9b01-b5576866a4b7 repro general protection fault in task_work_cancel_match 2026/03/07 19:59 2026/03/07 19:59 2026/03/07 20:08 31e9c887f7dc24e04b3ca70d0d54fc34141844b0
Discussions (1)
Title Replies (including bot) Last reply
[PATCH v1] landlock/tsync: fix null-ptr-deref in cancel_tsync_works() 3 (3) 2026/03/10 13:00

Sample crash report:
Oops: general protection fault, probably for non-canonical address 0xdffffc000000013c: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x00000000000009e0-0x00000000000009e7]
CPU: 1 UID: 0 PID: 14504 Comm: syz.3.2851 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+0x86/0x250 kernel/task_work.c:124
Code: 40 04 00 f3 f3 f3 65 48 8b 05 8e 99 3c 12 48 89 44 24 70 31 c0 e8 7a 89 37 00 4c 89 f8 48 c7 44 24 38 00 00 00 00 48 c1 e8 03 <42> 80 3c 30 00 0f 85 7e 01 00 00 4c 8b b3 e0 09 00 00 4d 85 f6 75
RSP: 0018:ffffc90003957ba0 EFLAGS: 00010206
RAX: 000000000000013c RBX: 0000000000000000 RCX: ffffffff84b87d7b
RDX: ffff8880581b0000 RSI: ffffffff81d14686 RDI: 0000000000000000
RBP: 1ffff9200072af77 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000000 R12: ffffffff81d14220
R13: ffff888029bd25c0 R14: dffffc0000000000 R15: 00000000000009e0
FS:  00007fa6327e06c0(0000) GS:ffff888124442000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000034042000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 task_work_cancel+0x23/0x30 kernel/task_work.c:187
 cancel_tsync_works security/landlock/tsync.c:415 [inline]
 landlock_restrict_sibling_threads+0xafe/0x1280 security/landlock/tsync.c:533
 __do_sys_landlock_restrict_self+0x5c9/0x9e0 security/landlock/syscalls.c:574
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa63199c799
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:00007fa6327e0028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be
RAX: ffffffffffffffda RBX: 00007fa631c15fa0 RCX: 00007fa63199c799
RDX: 0000000000000000 RSI: 000000000000000e RDI: 0000000000000003
RBP: 00007fa631a32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa631c16038 R14: 00007fa631c15fa0 R15: 00007ffffccb6028
 </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+0x86/0x250 kernel/task_work.c:124
Code: 40 04 00 f3 f3 f3 65 48 8b 05 8e 99 3c 12 48 89 44 24 70 31 c0 e8 7a 89 37 00 4c 89 f8 48 c7 44 24 38 00 00 00 00 48 c1 e8 03 <42> 80 3c 30 00 0f 85 7e 01 00 00 4c 8b b3 e0 09 00 00 4d 85 f6 75
RDX: ffff8880581b0000 RSI: ffffffff81d14686 RDI: 0000000000000000
RBP: 1ffff9200072af77 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000000 R12: ffffffff81d14220
R13: ffff888029bd25c0 R14: dffffc0000000000 R15: 00000000000009e0
FS:  00007fa6327e06c0(0000) GS:ffff888124442000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffe70 CR3: 0000000034042000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	40 04 00             	rex add $0x0,%al
   3:	f3 f3 f3 65 48 8b 05 	repz repz repz mov %gs:0x123c998e(%rip),%rax        # 0x123c999c
   a:	8e 99 3c 12
   e:	48 89 44 24 70       	mov    %rax,0x70(%rsp)
  13:	31 c0                	xor    %eax,%eax
  15:	e8 7a 89 37 00       	call   0x378994
  1a:	4c 89 f8             	mov    %r15,%rax
  1d:	48 c7 44 24 38 00 00 	movq   $0x0,0x38(%rsp)
  24:	00 00
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 30 00       	cmpb   $0x0,(%rax,%r14,1) <-- trapping instruction
  2f:	0f 85 7e 01 00 00    	jne    0x1b3
  35:	4c 8b b3 e0 09 00 00 	mov    0x9e0(%rbx),%r14
  3c:	4d 85 f6             	test   %r14,%r14
  3f:	75                   	.byte 0x75

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/21 01:55 upstream c612261bedd6 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root general protection fault in task_work_cancel_match
2026/03/19 23:08 upstream 8a30aeb0d1b4 bd6dcb30 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root general protection fault in task_work_cancel_match
2026/03/17 00:51 upstream 2d1373e4246d 0737c18f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root general protection fault in task_work_cancel_match
2026/03/10 09:35 upstream 1f318b96cc84 6972f302 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root general protection fault in task_work_cancel_match
2026/02/26 10:53 upstream d9d32e5bd5a4 e0f78d93 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root general protection fault in task_work_cancel_match
2026/02/16 04:42 upstream 26a4cfaff82a 1e62d198 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream general protection fault in task_work_cancel_match
2026/03/16 01:05 upstream 4f3df2e5ea69 ee8d34d6 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 general protection fault in task_work_cancel_match
2026/03/14 09:10 upstream 1c9982b49613 ee8d34d6 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 general protection fault in task_work_cancel_match
2026/03/14 08:46 upstream 1c9982b49613 ee8d34d6 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 general protection fault in task_work_cancel_match
2026/03/11 07:55 upstream b4f0dd314b39 86914af9 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 general protection fault in task_work_cancel_match
* Struck through repros no longer work on HEAD.