general protection fault in __bch2_trans_commit

[Ubisectech Sirius]

Hello.
We are Ubisectech Sirius Team, the vulnerability lab of China ValiantSec. Recently, our team has discovered a issue in Linux kernel 6.7. Attached to the email were a PoC file of the issue.

Stack dump:
general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 0 PID: 10008 Comm: syz-executor.3 Not tainted 6.7.0 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:bch2_snapshot_is_internal_node fs/bcachefs/snapshot.h:143 [inline]
RIP: 0010:btree_insert_entry_checks fs/bcachefs/btree_trans_commit.c:318 [inline]
RIP: 0010:__bch2_trans_commit+0x1630/0x6d60 fs/bcachefs/btree_trans_commit.c:1060
Code: 26 5b c7 fd 8b 85 e8 fe ff ff 85 c0 0f 85 2d 3b 00 00 e8 73 5f c7 fd 41 f7 d4 49 6b c4 38 49 8d 7c 06 14 48 89 f8 48 c1 e8 03 <0f> b6 14 18 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 ea
RSP: 0018:ffffc90002437378 EFLAGS: 00010203
RAX: 0000000000000002 RBX: dffffc0000000000 RCX: ffffc90005fa2000
RDX: 0000000000040000 RSI: ffffffff83c296dd RDI: 0000000000000014
RBP: ffffc90002437550 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: ffffffff83c29668 R12: 0000000000000000
R13: ffff88804c65a558 R14: 0000000000000000 R15: ffff88804c65a560
FS:  00007ffb04b55640(0000) GS:ffff88802c600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f48f35daf88 CR3: 000000005ca2c000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <TASK>
 bch2_trans_commit fs/bcachefs/btree_update.h:137 [inline]
 __bch2_create+0x857/0xeb0 fs/bcachefs/fs.c:280
 bch2_mknod fs/bcachefs/fs.c:379 [inline]
 bch2_create+0x41/0xc0 fs/bcachefs/fs.c:393
 lookup_open.isra.0+0xfc9/0x1370 fs/namei.c:3477
 open_last_lookups fs/namei.c:3546 [inline]
 path_openat+0xa89/0x26d0 fs/namei.c:3776
 do_filp_open+0x1c9/0x420 fs/namei.c:3809
 do_sys_openat2+0x164/0x1d0 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_creat fs/open.c:1528 [inline]
 __se_sys_creat fs/open.c:1522 [inline]
 __x64_sys_creat+0xcd/0x120 fs/open.c:1522
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x43/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7ffb03e8fd6d
Code: c3 e8 97 2b 00 00 0f 1f 80 00 00 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffb04b55028 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007ffb03fcbf80 RCX: 00007ffb03e8fd6d
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000480
RBP: 00007ffb03ef14cd R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007ffb03fcbf80 R15: 00007ffb04b35000
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:bch2_snapshot_is_internal_node fs/bcachefs/snapshot.h:143 [inline]
RIP: 0010:btree_insert_entry_checks fs/bcachefs/btree_trans_commit.c:318 [inline]
RIP: 0010:__bch2_trans_commit+0x1630/0x6d60 fs/bcachefs/btree_trans_commit.c:1060
Code: 26 5b c7 fd 8b 85 e8 fe ff ff 85 c0 0f 85 2d 3b 00 00 e8 73 5f c7 fd 41 f7 d4 49 6b c4 38 49 8d 7c 06 14 48 89 f8 48 c1 e8 03 <0f> b6 14 18 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 ea
RSP: 0018:ffffc90002437378 EFLAGS: 00010203
RAX: 0000000000000002 RBX: dffffc0000000000 RCX: ffffc90005fa2000
RDX: 0000000000040000 RSI: ffffffff83c296dd RDI: 0000000000000014
RBP: ffffc90002437550 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: ffffffff83c29668 R12: 0000000000000000
R13: ffff88804c65a558 R14: 0000000000000000 R15: ffff88804c65a560
FS:  00007ffb04b55640(0000) GS:ffff88802c600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f48f34f56c6 CR3: 000000005ca2c000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
----------------
Code disassembly (best guess), 3 bytes skipped:
   0:   fd                      std
   1:   8b 85 e8 fe ff ff       mov    -0x118(%rbp),%eax
   7:   85 c0                   test   %eax,%eax
   9:   0f 85 2d 3b 00 00       jne    0x3b3c
   f:   e8 73 5f c7 fd          call   0xfdc75f87
  14:   41 f7 d4                not    %r12d
  17:   49 6b c4 38             imul   $0x38,%r12,%rax
  1b:   49 8d 7c 06 14          lea    0x14(%r14,%rax,1),%rdi
  20:   48 89 f8                mov    %rdi,%rax
  23:   48 c1 e8 03             shr    $0x3,%rax
* 27:   0f b6 14 18             movzbl (%rax,%rbx,1),%edx <-- trapping instruction
  2b:   48 89 f8                mov    %rdi,%rax
  2e:   83 e0 07                and    $0x7,%eax
  31:   83 c0 03                add    $0x3,%eax
  34:   38 d0                   cmp    %dl,%al
  36:   7c 08                   jl     0x40
  38:   84 d2                   test   %dl,%dl
  3a:   0f                      .byte 0xf
  3b:   85 ea                   test   %ebp,%edx

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

Attachment: poc.c
Description: Binary data