# CVE-2023-54127: fs/jfs: prevent double-free in dbUnmount() after failed jfs_remount()

> A double-free vulnerability in the Linux kernel JFS filesystem allows local attackers to cause a denial of service or potentially execute arbitrary code.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2023-54127, DEBIAN-CVE-2023-54127, GHSA-pfr2-326c-2j2w, UBUNTU-CVE-2023-54127

## What is CVE-2023-54127?

CVE-2023-54127 is a high-severity use after free vulnerability in Linux, published on 24 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

fs/jfs: prevent double-free in dbUnmount() after failed jfs_remount()

Syzkaller reported the following issue:
==================================================================
BUG: KASAN: double-free in slab_free mm/slub.c:3787 [inline]
BUG: KASAN: double-free in __kmem_cache_free+0x71/0x110 mm/slub.c:3800
Free of addr ffff888086408000 by task syz-executor.4/12750
[...]
Call Trace:
 <TASK>
[...]
 kasan_report_invalid_free+0xac/0xd0 mm/kasan/report.c:482
 ____kasan_slab_free+0xfb/0x120
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1781 [inline]
 slab_free_freelist_hook+0x12e/0x1a0 mm/slub.c:1807
 slab_free mm/slub.c:3787 [inline]
 __kmem_cache_free+0x71/0x110 mm/slub.c:3800
 dbUnmount+0xf4/0x110 fs/jfs/jfs_dmap.c:264
 jfs_umount+0x248/0x3b0 fs/jfs/jfs_umount.c:87
 jfs_put_super+0x86/0x190 fs/jfs/super.c:194
 generic_shutdown_super+0x130/0x310 fs/super.c:492
 kill_block_super+0x79/0xd0 fs/super.c:1386
 deactivate_locked_super+0xa7/0xf0 fs/super.c:332
 cleanup_mnt+0x494/0x520 fs/namespace.c:1291
 task_work_run+0x243/0x300 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x124/0x150 kernel/entry/common.c:171
 exit_to_user_mode_prepare+0xb2/0x140 kernel/entry/common.c:203
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x26/0x60 kernel/entry/common.c:296
 do_syscall_64+0x49/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
[...]
 </TASK>

Allocated by task 13352:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x3d/0x60 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:371 [inline]
 __kasan_kmalloc+0x97/0xb0 mm/kasan/common.c:380
 kmalloc include/linux/slab.h:580 [inline]
 dbMount+0x54/0x980 fs/jfs/jfs_dmap.c:164
 jfs_mount+0x1dd/0x830 fs/jfs/jfs_mount.c:121
 jfs_fill_super+0x590/0xc50 fs/jfs/super.c:556
 mount_bdev+0x26c/0x3a0 fs/super.c:1359
 legacy_get_tree+0xea/0x180 fs/fs_context.c:610
 vfs_get_tree+0x88/0x270 fs/super.c:1489
 do_new_mount+0x289/0xad0 fs/namespace.c:3145
 do_mount fs/namespace.c:3488 [inline]
 __do_sys_mount fs/namespace.c:3697 [inline]
 __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 13352:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x3d/0x60 mm/kasan/common.c:52
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:518
 ____kasan_slab_free+0xd6/0x120 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1781 [inline]
 slab_free_freelist_hook+0x12e/0x1a0 mm/slub.c:1807
 slab_free mm/slub.c:3787 [inline]
 __kmem_cache_free+0x71/0x110 mm/slub.c:3800
 dbUnmount+0xf4/0x110 fs/jfs/jfs_dmap.c:264
 jfs_mount_rw+0x545/0x740 fs/jfs/jfs_mount.c:247
 jfs_remount+0x3db/0x710 fs/jfs/super.c:454
 reconfigure_super+0x3bc/0x7b0 fs/super.c:935
 vfs_fsconfig_locked fs/fsopen.c:254 [inline]
 __do_sys_fsconfig fs/fsopen.c:439 [inline]
 __se_sys_fsconfig+0xad5/0x1060 fs/fsopen.c:314
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
[...]

JFS_SBI(ipbmap->i_sb)->bmap wasn't set to NULL after kfree() in
dbUnmount().

Syzkaller uses faultinject to reproduce this KASAN double-free
warning. The issue is triggered if either diMount() or dbMount() fail
in jfs_remount(), since diUnmount() or dbUnmount() already happened in
such a case - they will do double-free on next execution: jfs_umount
or jfs_remount.

Tested on both upstream and jfs-next by syzkaller.

## Which versions are affected by CVE-2023-54127?


## How do I fix CVE-2023-54127?

Apply the vendor's patch.

## Is CVE-2023-54127 being exploited?

There is no known exploitation of CVE-2023-54127 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-54127 and fix it if it is affected.

What it is: CVE-2023-54127 is a high-severity use after free vulnerability in Linux, published on 24 Dec 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2023-54127 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-54127/ (Markdown: https://insights.sbomify.com/CVE-2023-54127/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-54127
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-54127
- OSV: https://osv.dev/vulnerability/CVE-2023-54127

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-54127/
Summaries are generated and may contain mistakes; the official description above is the record.