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SMTP id 5b1f17b1804b1-485419d759amr56148725e9.9.1773147604978; Tue, 10 Mar 2026 06:00:04 -0700 (PDT) Received: from google.com ([2a00:79e0:288a:8:43dd:a0ed:65ba:bc74]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48541a6bc3bsm82523515e9.2.2026.03.10.06.00.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2026 06:00:04 -0700 (PDT) Date: Tue, 10 Mar 2026 13:59:59 +0100 From: =?utf-8?Q?G=C3=BCnther?= Noack To: syzbot Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, mic@digikod.net, miklos@szeredi.hu, penguin-kernel@i-love.sakura.ne.jp, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [fuse?] general protection fault in task_work_cancel Message-ID: References: <69abb4e3.050a0220.13f275.003d.GAE@google.com> <69acf111.050a0220.310d8.0003.GAE@google.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <69acf111.050a0220.310d8.0003.GAE@google.com> On Sat, Mar 07, 2026 at 07:46:25PM -0800, syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: 4ae12d8bd9a8 Merge tag 'kbuild-fixes-7.0-2' of git://git.k.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=17dc475a580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=779072223d02a312 > dashboard link: https://syzkaller.appspot.com/bug?extid=741e2278ef71fef03a10 > compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=130b075a580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/010ac4052aed/disk-4ae12d8b.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/2aad8bef9031/vmlinux-4ae12d8b.xz > kernel image: https://storage.googleapis.com/syzbot-assets/fd350ec4896a/bzImage-4ae12d8b.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+741e2278ef71fef03a10@syzkaller.appspotmail.com > > 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: 13249 Comm: syz.1.1775 Not tainted syzkaller #0 PREEMPT(full) > 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 17 fe 9f 00 48 83 3b 00 75 51 e8 > RSP: 0018:ffffc9000ddffb20 EFLAGS: 00010216 > RAX: ffffffff818fdfc3 RBX: 00000000000009e0 RCX: ffff88805d5c3d00 > RDX: 0000000000000000 RSI: ffff888032f5c540 RDI: 0000000000000000 > RBP: ffffc9000ddffbd0 R08: ffffc9000ddffc97 R09: 1ffff92001bbff92 > R10: dffffc0000000000 R11: fffff52001bbff93 R12: dffffc0000000000 > R13: 1ffff92001bbff68 R14: 0000000000000000 R15: 000000000000013c > FS: 00007f9c8a1cb6c0(0000) GS:ffff888125561000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000200000010000 CR3: 0000000059bf0000 CR4: 0000000000350ef0 > Call Trace: > > 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: 0033:0x7f9c8939c799 > 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:00007f9c8a1cb028 EFLAGS: 00000246 ORIG_RAX: 00000000000001be > RAX: ffffffffffffffda RBX: 00007f9c89616180 RCX: 00007f9c8939c799 > RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000003 > RBP: 00007f9c89432bd9 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007f9c89616218 R14: 00007f9c89616180 R15: 00007ffee5d65d48 > > 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 17 fe 9f 00 48 83 3b 00 75 51 e8 > RSP: 0018:ffffc9000ddffb20 EFLAGS: 00010216 > RAX: ffffffff818fdfc3 RBX: 00000000000009e0 RCX: ffff88805d5c3d00 > RDX: 0000000000000000 RSI: ffff888032f5c540 RDI: 0000000000000000 > RBP: ffffc9000ddffbd0 R08: ffffc9000ddffc97 R09: 1ffff92001bbff92 > R10: dffffc0000000000 R11: fffff52001bbff93 R12: dffffc0000000000 > R13: 1ffff92001bbff68 R14: 0000000000000000 R15: 000000000000013c > FS: 00007f9c8a1cb6c0(0000) GS:ffff888125561000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f810d34da08 CR3: 0000000059bf0000 CR4: 0000000000350ef0 > ---------------- > 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 17 fe 9f 00 call 0x9ffe50 > 39: 48 83 3b 00 cmpq $0x0,(%rbx) > 3d: 75 51 jne 0x90 > 3f: e8 .byte 0xe8 > > > --- > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. #syz fix: landlock: Fully release unused TSYNC work entries (See https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot)