syzbot


kernel BUG in balance_leaf

Status: upstream: reported C repro on 2025/12/26 19:48
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+63f00aebc78ccad3a684@syzkaller.appspotmail.com
First crash: 19d, last: 18d
Bug presence (2)
Date Name Commit Repro Result
2025/12/28 linux-6.6.y (ToT) 5fa4793a2d2d C [report] KASAN: use-after-free Write in leaf_paste_in_buffer
2025/12/28 upstream (ToT) d26143bb38e2 C Didn't crash
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 kernel BUG in balance_leaf (2) origin:lts-only -1 C 5 4d04h 26d 0/3 upstream: reported C repro on 2025/12/19 10:25
linux-4.14 kernel BUG in balance_leaf reiserfs -1 C 1 1072d 1102d 0/1 upstream: reported C repro on 2023/01/08 11:53
upstream kernel BUG in balance_leaf fs -1 C error done 16 754d 1106d 25/29 fixed on 2024/01/30 15:47
linux-5.15 kernel BUG in balance_leaf (2) origin:lts-only -1 C error 3 50d 226d 0/3 upstream: reported C repro on 2025/06/02 02:17
linux-4.19 kernel BUG in balance_leaf reiserfs -1 C error 1 1096d 1096d 0/1 upstream: reported C repro on 2023/01/13 23:48
linux-5.15 kernel BUG in balance_leaf -1 1 465d 465d 0/3 auto-obsoleted due to no activity on 2025/01/14 15:53
linux-6.1 kernel BUG in balance_leaf -1 4 997d 1007d 0/3 auto-obsoleted due to no activity on 2023/08/21 17:28
Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/01/07 23:40 2h06m fix candidate upstream OK (0) job log

Sample crash report:
REISERFS warning (device loop0): vs-13060 reiserfs_update_sd_size: stat data of object [2 6 0x0 SD] (nlink == 1) not found (pos 1)
REISERFS panic (device loop0): vs-12195 balance_leaf: CFR not initialized
------------[ cut here ]------------
kernel BUG at fs/reiserfs/prints.c:390!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 5945 Comm: syz.0.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__reiserfs_panic+0x13e/0x140 fs/reiserfs/prints.c:390
Code: c7 c1 00 85 bc 8a 48 0f 44 c8 4c 0f 44 f0 48 c7 c7 c0 85 bc 8a 4c 89 fe 4c 89 f2 49 89 d8 49 c7 c1 40 61 fc 96 e8 12 66 ff ff <0f> 0b 66 0f 1f 00 53 48 89 fb e8 63 cb 28 f7 48 c7 c7 40 8e bc 8a
RSP: 0018:ffffc9000358e700 EFLAGS: 00010246
RAX: 0000000000000049 RBX: ffffffff8c583c48 RCX: 3f981bdd276f2400
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc9000358e7f0 R08: ffffc9000358e407 R09: 1ffff920006b1c80
R10: dffffc0000000000 R11: fffff520006b1c81 R12: ffffffff8abc2780
R13: ffffc9000358e720 R14: ffffffff8abc2760 R15: ffff888078a6c660
FS:  00007f33007986c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3300798d58 CR3: 0000000076b73000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 balance_leaf+0xd301/0x10da0 fs/reiserfs/do_balan.c:1439
 do_balance+0x2fe/0x940 fs/reiserfs/do_balan.c:1888
 reiserfs_paste_into_item+0x6a1/0x7f0 fs/reiserfs/stree.c:2157
 reiserfs_get_block+0x1bd3/0x3ed0 fs/reiserfs/inode.c:1069
 __block_write_begin_int+0x566/0x1ad0 fs/buffer.c:2124
 reiserfs_write_begin+0x20a/0x4c0 fs/reiserfs/inode.c:2771
 generic_perform_write+0x2fb/0x5b0 mm/filemap.c:4031
 generic_file_write_iter+0xaf/0x2e0 mm/filemap.c:4152
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x43b/0x940 fs/read_write.c:584
 ksys_write+0x147/0x250 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f32ff98f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3300798038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f32ffbe6090 RCX: 00007f32ff98f749
RDX: 0000000000001006 RSI: 00002000000007c0 RDI: 0000000000000007
RBP: 00007f32ffa13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f32ffbe6128 R14: 00007f32ffbe6090 R15: 00007ffd590aeb88
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__reiserfs_panic+0x13e/0x140 fs/reiserfs/prints.c:390
Code: c7 c1 00 85 bc 8a 48 0f 44 c8 4c 0f 44 f0 48 c7 c7 c0 85 bc 8a 4c 89 fe 4c 89 f2 49 89 d8 49 c7 c1 40 61 fc 96 e8 12 66 ff ff <0f> 0b 66 0f 1f 00 53 48 89 fb e8 63 cb 28 f7 48 c7 c7 40 8e bc 8a
RSP: 0018:ffffc9000358e700 EFLAGS: 00010246
RAX: 0000000000000049 RBX: ffffffff8c583c48 RCX: 3f981bdd276f2400
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc9000358e7f0 R08: ffffc9000358e407 R09: 1ffff920006b1c80
R10: dffffc0000000000 R11: fffff520006b1c81 R12: ffffffff8abc2780
R13: ffffc9000358e720 R14: ffffffff8abc2760 R15: ffff888078a6c660
FS:  00007f33007986c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdaa65f7e9c CR3: 0000000076b73000 CR4: 00000000003506f0

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/26 22:56 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan kernel BUG in balance_leaf
2025/12/26 19:48 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan kernel BUG in balance_leaf
2025/12/26 19:47 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan kernel BUG in balance_leaf
* Struck through repros no longer work on HEAD.