syzbot


general protection fault in balance_internal

Status: upstream: reported C repro on 2026/05/31 12:48
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+4e25c29d707d5868227f@syzkaller.appspotmail.com
First crash: 9d13h, last: 1d12h
Bug presence (2)
Date Name Commit Repro Result
2026/06/08 linux-5.15.y (ToT) dc027a595035 C [report] general protection fault in balance_internal
2026/06/08 upstream (ToT) 4549871118cf C Didn't crash
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 BUG: unable to handle kernel paging request in balance_internal 8 C 10 1d21h 71d 0/3 upstream: reported C repro on 2026/03/30 03:10

Sample crash report:
REISERFS warning (device loop0): vs-13060 reiserfs_update_sd_size: stat data of object [2 2 0x0 SD] (nlink == 1) not found (pos 0)
REISERFS warning (device loop0): vs-13060 reiserfs_update_sd_size: stat data of object [2 2 0x0 SD] (nlink == 1) not found (pos 0)
general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
CPU: 0 PID: 4323 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:balance_internal_when_delete fs/reiserfs/ibalance.c:675 [inline]
RIP: 0010:balance_internal+0x290e/0x4ab0 fs/reiserfs/ibalance.c:849
Code: 48 4c 89 f0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 f7 e8 95 2f bf ff 49 8b 06 48 89 44 24 20 48 8d 58 18 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 73 2f bf ff 44 8b 33 48 b8 00 00
RSP: 0018:ffffc90002feeb00 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff88802187d940
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90002feed90 R08: ffff888140a9e82f R09: 1ffff11028153d05
R10: dffffc0000000000 R11: ffffed1028153d06 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffc90002feefc8 R15: ffffc90002feef80
FS:  0000555562b2d500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f26d9819000 CR3: 000000001fcac000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_balance+0x36e/0x930 fs/reiserfs/do_balan.c:1896
 reiserfs_delete_solid_item+0x94a/0xfa0 fs/reiserfs/stree.c:1462
 remove_save_link+0x254/0x3e0 fs/reiserfs/super.c:540
 reiserfs_truncate_file+0x7c9/0xe40 fs/reiserfs/inode.c:2330
 reiserfs_setattr+0xab3/0x1090 fs/reiserfs/inode.c:3409
 notify_change+0xbcd/0xee0 fs/attr.c:505
 do_truncate+0x1ac/0x240 fs/open.c:65
 handle_truncate fs/namei.c:3273 [inline]
 do_open fs/namei.c:3620 [inline]
 path_openat+0x2922/0x2fa0 fs/namei.c:3750
 do_filp_open+0x1e2/0x410 fs/namei.c:3777
 do_sys_openat2+0x150/0x4b0 fs/open.c:1255
 do_sys_open fs/open.c:1271 [inline]
 __do_sys_open fs/open.c:1279 [inline]
 __se_sys_open fs/open.c:1275 [inline]
 __x64_sys_open+0x11b/0x140 fs/open.c:1275
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fdc70d17e59
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:00007ffc979ac208 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007fdc70f90fa0 RCX: 00007fdc70d17e59
RDX: 000000000000012a RSI: 0000000000000200 RDI: 00002000000001c0
RBP: 00007fdc70dadd6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdc70f90fac R14: 00007fdc70f90fa0 R15: 00007fdc70f90fa0
 </TASK>
Modules linked in:
---[ end trace 36aa36403eb78e5a ]---
RIP: 0010:balance_internal_when_delete fs/reiserfs/ibalance.c:675 [inline]
RIP: 0010:balance_internal+0x290e/0x4ab0 fs/reiserfs/ibalance.c:849
Code: 48 4c 89 f0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 f7 e8 95 2f bf ff 49 8b 06 48 89 44 24 20 48 8d 58 18 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 74 08 48 89 df e8 73 2f bf ff 44 8b 33 48 b8 00 00
RSP: 0018:ffffc90002feeb00 EFLAGS: 00010206
RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff88802187d940
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90002feed90 R08: ffff888140a9e82f R09: 1ffff11028153d05
R10: dffffc0000000000 R11: ffffed1028153d06 R12: 0000000000000000
R13: dffffc0000000000 R14: ffffc90002feefc8 R15: ffffc90002feef80
FS:  0000555562b2d500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f26d9819000 CR3: 000000001fcac000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	48                   	rex.W
   1:	4c 89 f0             	mov    %r14,%rax
   4:	48 c1 e8 03          	shr    $0x3,%rax
   8:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1)
   d:	74 08                	je     0x17
   f:	4c 89 f7             	mov    %r14,%rdi
  12:	e8 95 2f bf ff       	call   0xffbf2fac
  17:	49 8b 06             	mov    (%r14),%rax
  1a:	48 89 44 24 20       	mov    %rax,0x20(%rsp)
  1f:	48 8d 58 18          	lea    0x18(%rax),%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 73 2f bf ff       	call   0xffbf2fac
  39:	44 8b 33             	mov    (%rbx),%r14d
  3c:	48                   	rex.W
  3d:	b8                   	.byte 0xb8

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/31 14:03 linux-5.15.y 241d66fa280c 6b4a8443 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-5-15-kasan general protection fault in balance_internal
2026/05/31 13:27 linux-5.15.y 241d66fa280c 6b4a8443 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-5-15-kasan general protection fault in balance_internal
2026/05/31 12:48 linux-5.15.y 241d66fa280c 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan general protection fault in balance_internal
* Struck through repros no longer work on HEAD.