Hello.
We are Ubisectech Sirius Team, the vulnerability lab of China ValiantSec. Recently, our team has discovered a issue in Linux kernel 6.11.0-rc2-g6a0e38264012. Attached to the email were a PoC file of the issue.

Stack dump:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
CPU: 0 UID: 0 PID: 14256 Comm: syz.1.435 Not tainted 6.11.0-rc2-g6a0e38264012 #49
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:perf_trace_block_buffer+0x232/0x590 include/trace/events/block.h:24
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 5f 02 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 56 30 48 8d 7a 34 48 89 f9 48 c1 e9 03 <0f> b6 0c 01 48 89 f8 83 e0 07 83 c0 03 38 c8 7c 08 84 c9 0f 85 9c
RSP: 0018:ffffc90001957818 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffffe8ffad633a98 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 1ffff110058c6f97 RDI: 0000000000000034
RBP: ffffc900019578d8 R08: 0000000000000004 R09: 0000000000000004
R10: ffffe8ffad6ba000 R11: 0000000000000001 R12: 1ffff9200032af06
R13: ffffffff8e3a3fe0 R14: ffff88801fb7e2b8 R15: ffffc900019578b0
FS:  00007f6a432a0640(0000) GS:ffff88802c600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005614bbc3d038 CR3: 000000004c664000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <TASK>
 trace_block_touch_buffer include/trace/events/block.h:54 [inline]
 touch_buffer+0x178/0x250 fs/buffer.c:64
 __nilfs_get_folio_block fs/nilfs2/page.c:42 [inline]
 nilfs_grab_buffer+0x1bb/0x380 fs/nilfs2/page.c:61
 nilfs_mdt_submit_block+0xa4/0x870 fs/nilfs2/mdt.c:121
 nilfs_mdt_read_block+0x92/0x3c0 fs/nilfs2/mdt.c:176
 nilfs_mdt_get_block+0xd2/0xaa0 fs/nilfs2/mdt.c:251
 nilfs_cpfile_get_checkpoint_block fs/nilfs2/cpfile.c:139 [inline]
 nilfs_cpfile_set_snapshot fs/nilfs2/cpfile.c:763 [inline]
 nilfs_cpfile_change_cpmode+0x19f/0x1b70 fs/nilfs2/cpfile.c:1055
 nilfs_ioctl_change_cpmode fs/nilfs2/ioctl.c:209 [inline]
 nilfs_ioctl+0x64f/0x1720 fs/nilfs2/ioctl.c:1278
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __x64_sys_ioctl+0x1a1/0x210 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcb/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6a4259712d
Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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:00007f6a4329ff98 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6a42735f80 RCX: 00007f6a4259712d
RDX: 0000000020000080 RSI: 0000000040106e80 RDI: 000000000000000c
RBP: 00007f6a4261bd8a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f6a42735f80 R15: 00007f6a43280000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:perf_trace_block_buffer+0x232/0x590 include/trace/events/block.h:24
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 5f 02 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 56 30 48 8d 7a 34 48 89 f9 48 c1 e9 03 <0f> b6 0c 01 48 89 f8 83 e0 07 83 c0 03 38 c8 7c 08 84 c9 0f 85 9c
RSP: 0018:ffffc90001957818 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffffe8ffad633a98 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 1ffff110058c6f97 RDI: 0000000000000034
RBP: ffffc900019578d8 R08: 0000000000000004 R09: 0000000000000004
R10: ffffe8ffad6ba000 R11: 0000000000000001 R12: 1ffff9200032af06
R13: ffffffff8e3a3fe0 R14: ffff88801fb7e2b8 R15: ffffc900019578b0
FS:  00007f6a432a0640(0000) GS:ffff88802c600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005614bbc3d038 CR3: 000000004c664000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
----------------
Code disassembly (best guess):
   0:   48 89 fa                mov    %rdi,%rdx
   3:   48 c1 ea 03             shr    $0x3,%rdx
   7:   80 3c 02 00             cmpb   $0x0,(%rdx,%rax,1)
   b:   0f 85 5f 02 00 00       jne    0x270
  11:   48 b8 00 00 00 00 00    movabs $0xdffffc0000000000,%rax
  18:   fc ff df
  1b:   49 8b 56 30             mov    0x30(%r14),%rdx
  1f:   48 8d 7a 34             lea    0x34(%rdx),%rdi
  23:   48 89 f9                mov    %rdi,%rcx
  26:   48 c1 e9 03             shr    $0x3,%rcx
* 2a:   0f b6 0c 01             movzbl (%rcx,%rax,1),%ecx <-- trapping instruction
  2e:   48 89 f8                mov    %rdi,%rax
  31:   83 e0 07                and    $0x7,%eax
  34:   83 c0 03                add    $0x3,%eax
  37:   38 c8                   cmp    %cl,%al
  39:   7c 08                   jl     0x43
  3b:   84 c9                   test   %cl,%cl
  3d:   0f                      .byte 0xf
  3e:   85                      .byte 0x85
  3f:   9c                      pushf

Thank you for taking the time to read this email and we look forward to working with you further.