linux-kernel - Re: [syzbot] [jfs?] kernel BUG in dtSplitRoot

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Message-ID: <69350d1a.a70a0220.38f243.0043.GAE@google.com>
Date: Sat, 06 Dec 2025 21:14:02 -0800
From: syzbot <syzbot+a099d674daa27a9272db@...kaller.appspotmail.com>
To: kartikey406@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [jfs?] kernel BUG in dtSplitRoot

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
general protection fault in txCommit

UFO tlock:0xffffc9000152a678
UFO tlock:0xffffc9000152a3a8
UFO tlock:0xffffc9000152a090
UFO tlock:0xffffc9000152a750
UFO tlock:0xffffc9000152a438
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000005: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f]
CPU: 0 UID: 0 PID: 6367 Comm: syz.0.152 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:txLog fs/jfs/jfs_txnmgr.c:1395 [inline]
RIP: 0010:txCommit+0xafb/0x5430 fs/jfs/jfs_txnmgr.c:1270
Code: 3c 10 00 74 12 4c 89 f7 e8 72 e1 db fe 48 ba 00 00 00 00 00 fc ff df 4c 89 74 24 68 4d 8b 36 4d 8d 7e 28 4c 89 f8 48 c1 e8 03 <80> 3c 10 00 74 12 4c 89 ff e8 47 e1 db fe 48 ba 00 00 00 00 00 fc
RSP: 0018:ffffc900036f7540 EFLAGS: 00010206
RAX: 0000000000000005 RBX: 00000000000009d8 RCX: 1ffff920002a5dd8
RDX: dffffc0000000000 RSI: 0000000000000000 RDI: ffffc9000152a807
RBP: ffffc900036f7710 R08: ffffc900036f7447 R09: 1ffff920006dee88
R10: dffffc0000000000 R11: fffff520006dee89 R12: ffffc9000152a7e6
R13: ffffc9000152a000 R14: 0000000000000000 R15: 0000000000000028
FS:  00007f6c1239e6c0(0000) GS:ffff88808d239000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd6871fb000 CR3: 0000000053d52000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 jfs_create+0x865/0xa80 fs/jfs/namei.c:156
 lookup_open fs/namei.c:4440 [inline]
 open_last_lookups fs/namei.c:4540 [inline]
 path_openat+0x18bb/0x3dd0 fs/namei.c:4784
 do_filp_open+0x1fa/0x410 fs/namei.c:4814
 do_sys_openat2+0x121/0x200 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_creat fs/open.c:1514 [inline]
 __se_sys_creat fs/open.c:1508 [inline]
 __x64_sys_creat+0x8f/0xc0 fs/open.c:1508
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6c1158f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6c1239e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007f6c117e5fa0 RCX: 00007f6c1158f7c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000580
RBP: 00007f6c11613f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6c117e6038 R14: 00007f6c117e5fa0 R15: 00007ffff4918648
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:txLog fs/jfs/jfs_txnmgr.c:1395 [inline]
RIP: 0010:txCommit+0xafb/0x5430 fs/jfs/jfs_txnmgr.c:1270
Code: 3c 10 00 74 12 4c 89 f7 e8 72 e1 db fe 48 ba 00 00 00 00 00 fc ff df 4c 89 74 24 68 4d 8b 36 4d 8d 7e 28 4c 89 f8 48 c1 e8 03 <80> 3c 10 00 74 12 4c 89 ff e8 47 e1 db fe 48 ba 00 00 00 00 00 fc
RSP: 0018:ffffc900036f7540 EFLAGS: 00010206
RAX: 0000000000000005 RBX: 00000000000009d8 RCX: 1ffff920002a5dd8
RDX: dffffc0000000000 RSI: 0000000000000000 RDI: ffffc9000152a807
RBP: ffffc900036f7710 R08: ffffc900036f7447 R09: 1ffff920006dee88
R10: dffffc0000000000 R11: fffff520006dee89 R12: ffffc9000152a7e6
R13: ffffc9000152a000 R14: 0000000000000000 R15: 0000000000000028
FS:  00007f6c1239e6c0(0000) GS:ffff88808d239000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fba0d9a0000 CR3: 0000000053d52000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	3c 10                	cmp    $0x10,%al
   2:	00 74 12 4c          	add    %dh,0x4c(%rdx,%rdx,1)
   6:	89 f7                	mov    %esi,%edi
   8:	e8 72 e1 db fe       	call   0xfedbe17f
   d:	48 ba 00 00 00 00 00 	movabs $0xdffffc0000000000,%rdx
  14:	fc ff df
  17:	4c 89 74 24 68       	mov    %r14,0x68(%rsp)
  1c:	4d 8b 36             	mov    (%r14),%r14
  1f:	4d 8d 7e 28          	lea    0x28(%r14),%r15
  23:	4c 89 f8             	mov    %r15,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 10 00          	cmpb   $0x0,(%rax,%rdx,1) <-- trapping instruction
  2e:	74 12                	je     0x42
  30:	4c 89 ff             	mov    %r15,%rdi
  33:	e8 47 e1 db fe       	call   0xfedbe17f
  38:	48                   	rex.W
  39:	ba 00 00 00 00       	mov    $0x0,%edx
  3e:	00 fc                	add    %bh,%ah


Tested on:

commit:         37bb2e72 Merge tag 'staging-6.19-rc1' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13a4a6c2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1889d7812b50029c
dashboard link: https://syzkaller.appspot.com/bug?extid=a099d674daa27a9272db
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=159e4eb4580000