kernel BUG in dbBackSplit (2)

Status: upstream: reported on 2026/01/09 20:35
Subsystems: jfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+5391ade36343d8cd8801@syzkaller.appspotmail.com
First crash: 229d, last: 1d20h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
feaf719c assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ kernel BUG in dbBackSplit (2) 2026/05/21 14:43 2026/05/21 14:43 2026/05/21 15:25 d5742584
945dd1d2 repro kernel BUG in dbBackSplit (2) 2026/03/10 13:48 2026/03/11 12:40 2026/03/11 13:04 86914af9
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [jfs?] kernel BUG in dbBackSplit (2) 0 (1) 2026/01/09 20:35
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream kernel BUG in dbBackSplit jfs -1 2 710d 706d 0/29 auto-obsoleted due to no activity on 2024/12/20 17:49

Sample crash report:
loop0: detected capacity change from 0 to 32768

 ... Log Wrap ... Log Wrap ... Log Wrap ...

ERROR: (device loop0): diWrite: ixpxd invalid

ERROR: (device loop0): txCommit: 

ERROR: (device loop0): diWrite: ixpxd invalid

ERROR: (device loop0): txCommit: 

loop0: detected capacity change from 32768 to 32767
dmapctl: invalid nleafs 4294967295 (max 1024)
ERROR: (device loop0): dbAdjCtl: Corrupt dmapctl page

ERROR: (device loop0): dbDiscardAG: -EIO

dmapctl: invalid nleafs 4294967295 (max 1024)
ERROR: (device loop0): dbAdjCtl: Corrupt dmapctl page

BUG at fs/jfs/jfs_dmap.c:2787 assert(leaf[leafno] == NOFREE)
------------[ cut here ]------------
kernel BUG at fs/jfs/jfs_dmap.c:2787!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5316 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:dbBackSplit+0x57c/0x580 fs/jfs/jfs_dmap.c:2787
Code: e9 02 fc ff ff e8 d4 98 5c fe 48 c7 c7 a0 53 2d 8c 48 c7 c6 e0 50 2d 8c ba e3 0a 00 00 48 c7 c1 c0 5a 2d 8c e8 25 44 bd fd 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41
RSP: 0018:ffffc90001457bc0 EFLAGS: 00010246
RAX: 000000000000003c RBX: 000000000000000a RCX: f7095dce00ded400
RDX: ffffc9000e782000 RSI: 0000000000003044 RDI: 0000000000003045
RBP: 0000000000000000 R08: ffffc90001457947 R09: 1ffff9200028af28
R10: dffffc0000000000 R11: fffff5200028af29 R12: 0000000000000020
R13: ffff888043d05010 R14: ffff888043d05096 R15: ffff888043d05076
FS:  00007fc49f4e36c0(0000) GS:ffff88808c519000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc492e42000 CR3: 000000001275c000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 dbFreeDmap fs/jfs/jfs_dmap.c:2195 [inline]
 dbFree+0x53f/0x650 fs/jfs/jfs_dmap.c:485
 dbDiscardAG+0x7b5/0x8f0 fs/jfs/jfs_dmap.c:1732
 jfs_ioc_trim+0x436/0x680 fs/jfs/jfs_discard.c:106
 jfs_ioctl+0x28e/0x3b0 fs/jfs/ioctl.c:131
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc49e59e0d9
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:00007fc49f4e2fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc49e825fa0 RCX: 00007fc49e59e0d9
RDX: 0000200000000080 RSI: 00000000c0185879 RDI: 0000000000000006
RBP: 00007fc49e635024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc49e826038 R14: 00007fc49e825fa0 R15: 00007ffcffdf16f8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:dbBackSplit+0x57c/0x580 fs/jfs/jfs_dmap.c:2787
Code: e9 02 fc ff ff e8 d4 98 5c fe 48 c7 c7 a0 53 2d 8c 48 c7 c6 e0 50 2d 8c ba e3 0a 00 00 48 c7 c1 c0 5a 2d 8c e8 25 44 bd fd 90 <0f> 0b 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 55 41
RSP: 0018:ffffc90001457bc0 EFLAGS: 00010246
RAX: 000000000000003c RBX: 000000000000000a RCX: f7095dce00ded400
RDX: ffffc9000e782000 RSI: 0000000000003044 RDI: 0000000000003045
RBP: 0000000000000000 R08: ffffc90001457947 R09: 1ffff9200028af28
R10: dffffc0000000000 R11: fffff5200028af29 R12: 0000000000000020
R13: ffff888043d05010 R14: ffff888043d05096 R15: ffff888043d05076
FS:  00007fc49f4e36c0(0000) GS:ffff88808c519000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e2b18b8048 CR3: 000000001275c000 CR4: 0000000000352ef0

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/21 01:56 upstream 9d2ed026f031 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in dbBackSplit
2026/08/18 04:34 upstream ff68e5f557f6 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in dbBackSplit
2026/07/02 13:28 upstream 4a50a141f05a 27192279 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in dbBackSplit
2026/03/28 00:34 upstream 7df48e363130 f9ef2ec1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in dbBackSplit
2026/01/06 08:57 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in dbBackSplit
2026/01/05 20:24 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in dbBackSplit
* Struck through repros no longer work on HEAD.