Re: [syzbot] [jfs?] KMSAN: uninit-value in txLock

[syzbot <syzbot+d3a57c32b9112d7b01ec@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: unable to handle kernel NULL pointer dereference in __mark_inode_dirty

loop0: detected capacity change from 0 to 32768
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 800000001381f067 P4D 800000001381f067 PUD 0 
Oops: Oops: 0000 [#1] SMP PTI
CPU: 1 UID: 0 PID: 6507 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026
RIP: 0010:__list_del_entry_valid include/linux/list.h:127 [inline]
RIP: 0010:__list_del_entry include/linux/list.h:223 [inline]
RIP: 0010:list_move include/linux/list.h:306 [inline]
RIP: 0010:inode_io_list_move_locked+0x152/0x8d0 fs/fs-writeback.c:122
Code: 00 00 00 4d 8b b4 24 e8 00 00 00 48 89 7d a8 e8 54 34 cc ff 4c 8b 28 44 8b 3a 4d 85 ed 0f 85 bc 03 00 00 49 81 c4 e0 00 00 00 <49> 8b 1e 4c 89 f7 e8 33 34 cc ff 48 8b 00 48 85 c0 74 12 48 89 d9
RSP: 0018:ffff88803945b8c8 EFLAGS: 00010286
RAX: ffff88801ae0d7c8 RBX: 0000000000000000 RCX: 0000000000087a41
RDX: ffff88801b20d7c8 RSI: 0000000000000001 RDI: ffff88801b60d7c8
RBP: ffff88803945b930 R08: ffffea000000000f R09: 0000000000000000
R10: ffff88801ae0d760 R11: ffffffff844dab90 R12: ffff88801b60d7c0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f249ec6e6c0(0000) GS:ffff8881aadec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000004f37a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __mark_inode_dirty+0x878/0x1050 fs/fs-writeback.c:2668
 generic_update_time fs/inode.c:2158 [inline]
 inode_update_time fs/inode.c:2171 [inline]
 file_update_time_flags+0x9e7/0xa60 fs/inode.c:2398
 file_update_time+0x30/0x40 fs/inode.c:2419
 __generic_file_write_iter+0x124/0x460 mm/filemap.c:4412
 generic_file_write_iter+0x131/0x980 mm/filemap.c:4457
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0xbe1/0x15c0 fs/read_write.c:686
 ksys_pwrite64 fs/read_write.c:793 [inline]
 __do_sys_pwrite64 fs/read_write.c:801 [inline]
 __se_sys_pwrite64 fs/read_write.c:798 [inline]
 __x64_sys_pwrite64+0x2ab/0x3b0 fs/read_write.c:798
 x64_sys_call+0xbaf/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:19
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f249dd9aef9
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:00007f249ec6e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f249e005fa0 RCX: 00007f249dd9aef9
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007f249de2fee0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f249e006038 R14: 00007f249e005fa0 R15: 00007fff32808dd8
 </TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:__list_del_entry_valid include/linux/list.h:127 [inline]
RIP: 0010:__list_del_entry include/linux/list.h:223 [inline]
RIP: 0010:list_move include/linux/list.h:306 [inline]
RIP: 0010:inode_io_list_move_locked+0x152/0x8d0 fs/fs-writeback.c:122
Code: 00 00 00 4d 8b b4 24 e8 00 00 00 48 89 7d a8 e8 54 34 cc ff 4c 8b 28 44 8b 3a 4d 85 ed 0f 85 bc 03 00 00 49 81 c4 e0 00 00 00 <49> 8b 1e 4c 89 f7 e8 33 34 cc ff 48 8b 00 48 85 c0 74 12 48 89 d9
RSP: 0018:ffff88803945b8c8 EFLAGS: 00010286
RAX: ffff88801ae0d7c8 RBX: 0000000000000000 RCX: 0000000000087a41
RDX: ffff88801b20d7c8 RSI: 0000000000000001 RDI: ffff88801b60d7c8
RBP: ffff88803945b930 R08: ffffea000000000f R09: 0000000000000000
R10: ffff88801ae0d760 R11: ffffffff844dab90 R12: ffff88801b60d7c0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f249ec6e6c0(0000) GS:ffff8881aadec000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000004f37a000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	00 4d 8b             	add    %cl,-0x75(%rbp)
   5:	b4 24                	mov    $0x24,%ah
   7:	e8 00 00 00 48       	call   0x4800000c
   c:	89 7d a8             	mov    %edi,-0x58(%rbp)
   f:	e8 54 34 cc ff       	call   0xffcc3468
  14:	4c 8b 28             	mov    (%rax),%r13
  17:	44 8b 3a             	mov    (%rdx),%r15d
  1a:	4d 85 ed             	test   %r13,%r13
  1d:	0f 85 bc 03 00 00    	jne    0x3df
  23:	49 81 c4 e0 00 00 00 	add    $0xe0,%r12
* 2a:	49 8b 1e             	mov    (%r14),%rbx <-- trapping instruction
  2d:	4c 89 f7             	mov    %r14,%rdi
  30:	e8 33 34 cc ff       	call   0xffcc3468
  35:	48 8b 00             	mov    (%rax),%rax
  38:	48 85 c0             	test   %rax,%rax
  3b:	74 12                	je     0x4f
  3d:	48 89 d9             	mov    %rbx,%rcx


Tested on:

commit:         c072629f Merge tag 'v6.19-p4' of git://git.kernel.org/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10b857fc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=62c21fde37118981
dashboard link: https://syzkaller.appspot.com/bug?extid=d3a57c32b9112d7b01ec
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=147797fc580000