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

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Message-ID: <693513aa.a70a0220.38f243.0046.GAE@google.com>
Date: Sat, 06 Dec 2025 21:42:02 -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 dbFree

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: 104 Comm: jfsCommit 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:dbFree+0xba/0x650 fs/jfs/jfs_dmap.c:352
Code: c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 de 34 e0 fe 48 8b 03 48 89 44 24 10 48 8b 44 24 20 48 8d 78 28 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00 74 05 e8 ba 34 e0 fe 48 8b 44 24 20 48 8b 58 28 48
RSP: 0018:ffffc900018a7a98 EFLAGS: 00010206
RAX: 0000000000000005 RBX: ffff8880432eaea0 RCX: ffff88801c7ca4c0
RDX: 0000000000000000 RSI: 0000000000000022 RDI: 0000000000000028
RBP: 0000000000000001 R08: ffff88801c7ca4c0 R09: 0000000000000002
R10: 0000000000000040 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000022 R14: ffff888055b49fd0 R15: 1ffff1100ab693fa
FS:  0000000000000000(0000) GS:ffff88808d239000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f908a83f000 CR3: 0000000046fec000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 txFreeMap+0x7ff/0xde0 fs/jfs/jfs_txnmgr.c:2539
 txUpdateMap+0x308/0x9c0 fs/jfs/jfs_txnmgr.c:-1
 txLazyCommit fs/jfs/jfs_txnmgr.c:2669 [inline]
 jfs_lazycommit+0x43f/0xa90 fs/jfs/jfs_txnmgr.c:2738
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dbFree+0xba/0x650 fs/jfs/jfs_dmap.c:352
Code: c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 de 34 e0 fe 48 8b 03 48 89 44 24 10 48 8b 44 24 20 48 8d 78 28 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00 74 05 e8 ba 34 e0 fe 48 8b 44 24 20 48 8b 58 28 48
RSP: 0018:ffffc900018a7a98 EFLAGS: 00010206
RAX: 0000000000000005 RBX: ffff8880432eaea0 RCX: ffff88801c7ca4c0
RDX: 0000000000000000 RSI: 0000000000000022 RDI: 0000000000000028
RBP: 0000000000000001 R08: ffff88801c7ca4c0 R09: 0000000000000002
R10: 0000000000000040 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000022 R14: ffff888055b49fd0 R15: 1ffff1100ab693fa
FS:  0000000000000000(0000) GS:ffff88808d239000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa71adff000 CR3: 0000000047507000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess):
   0:	c1 e8 03             	shr    $0x3,%eax
   3:	42 80 3c 20 00       	cmpb   $0x0,(%rax,%r12,1)
   8:	74 08                	je     0x12
   a:	48 89 df             	mov    %rbx,%rdi
   d:	e8 de 34 e0 fe       	call   0xfee034f0
  12:	48 8b 03             	mov    (%rbx),%rax
  15:	48 89 44 24 10       	mov    %rax,0x10(%rsp)
  1a:	48 8b 44 24 20       	mov    0x20(%rsp),%rax
  1f:	48 8d 78 28          	lea    0x28(%rax),%rdi
  23:	48 89 f8             	mov    %rdi,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	42 80 3c 20 00       	cmpb   $0x0,(%rax,%r12,1) <-- trapping instruction
  2f:	74 05                	je     0x36
  31:	e8 ba 34 e0 fe       	call   0xfee034f0
  36:	48 8b 44 24 20       	mov    0x20(%rsp),%rax
  3b:	48 8b 58 28          	mov    0x28(%rax),%rbx
  3f:	48                   	rex.W


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=162efc1a580000
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=1386221a580000