[v6.1] general protection fault in __ext4_journal_get_write_access (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f6e38ae624cf Linux 6.1.158
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1579a57c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7eb38bd5021fec61
dashboard link: https://syzkaller.appspot.com/bug?extid=c890c084a63d534ab61b
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2b7003e2661d/disk-f6e38ae6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0696cea8d016/vmlinux-f6e38ae6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6b7a89e636d7/bzImage-f6e38ae6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c890c0...@syzkaller.appspotmail.com

general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
CPU: 0 PID: 4455 Comm: ext4lazyinit Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__ext4_journal_get_write_access+0xc6/0x6d0 fs/ext4/ext4_jbd2.c:231
Code: 31 c0 49 8d 5f 30 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 f8 86 b5 ff 48 8b 1b 48 83 c3 38 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 db 86 b5 ff 4c 8b 23 4d 85 e4 4c
RSP: 0018:ffffc90004387ba0 EFLAGS: 00010202
RAX: 0000000000000007 RBX: 0000000000000038 RCX: d662d970f4920300
RDX: ffff88802a87bb80 RSI: ffffffff8a8c1700 RDI: ffffffff8adef760
RBP: ffffc90004387c70 R08: ffff88805555bae0 R09: 0000000000000001
R10: ffffed100aa99835 R11: 1ffff1100aa99834 R12: 1ffff1100ed884cf
R13: dffffc0000000000 R14: 0000000000000001 R15: ffff88805555bae0
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f23d61b42f8 CR3: 000000005d30f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ext4_init_inode_table+0x3fa/0x7b0 fs/ext4/ialloc.c:1598
ext4_run_li_request fs/ext4/super.c:3682 [inline]
ext4_lazyinit_thread+0xba4/0x1800 fs/ext4/super.c:3773
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__ext4_journal_get_write_access+0xc6/0x6d0 fs/ext4/ext4_jbd2.c:231
Code: 31 c0 49 8d 5f 30 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 f8 86 b5 ff 48 8b 1b 48 83 c3 38 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 db 86 b5 ff 4c 8b 23 4d 85 e4 4c
RSP: 0018:ffffc90004387ba0 EFLAGS: 00010202
RAX: 0000000000000007 RBX: 0000000000000038 RCX: d662d970f4920300
RDX: ffff88802a87bb80 RSI: ffffffff8a8c1700 RDI: ffffffff8adef760
RBP: ffffc90004387c70 R08: ffff88805555bae0 R09: 0000000000000001
R10: ffffed100aa99835 R11: 1ffff1100aa99834 R12: 1ffff1100ed884cf
R13: dffffc0000000000 R14: 0000000000000001 R15: ffff88805555bae0
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f33f75b7198 CR3: 000000005d30f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 31 c0 xor %eax,%eax
2: 49 8d 5f 30 lea 0x30(%r15),%rbx
6: 48 89 d8 mov %rbx,%rax
9: 48 c1 e8 03 shr $0x3,%rax
d: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1)
12: 74 08 je 0x1c
14: 48 89 df mov %rbx,%rdi
17: e8 f8 86 b5 ff call 0xffb58714
1c: 48 8b 1b mov (%rbx),%rbx
1f: 48 83 c3 38 add $0x38,%rbx
23: 48 89 d8 mov %rbx,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 48 89 df mov %rbx,%rdi
34: e8 db 86 b5 ff call 0xffb58714
39: 4c 8b 23 mov (%rbx),%r12
3c: 4d 85 e4 test %r12,%r12
3f: 4c rex.WR


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