# CVE-2023-53846: f2fs: fix to do sanity check on direct node in truncate_dnode()

> A use-after-free vulnerability in the Linux kernel's f2fs filesystem allows local attackers to cause a system crash or potentially execute arbitrary code via crafted file operations.

- **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:** 9 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2023-53846, DEBIAN-CVE-2023-53846, GHSA-2r6x-xmcw-65m8, ROOT-OS-DEBIAN-11-CVE-2023-53846, ROOT-OS-DEBIAN-12-CVE-2023-53846, ROOT-OS-UBUNTU-2204-CVE-2023-53846, UBUNTU-CVE-2023-53846

## What is CVE-2023-53846?

CVE-2023-53846 is a high-severity use after free vulnerability in Linux, published on 9 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:

f2fs: fix to do sanity check on direct node in truncate_dnode()

syzbot reports below bug:

BUG: KASAN: slab-use-after-free in f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574
Read of size 4 at addr ffff88802a25c000 by task syz-executor148/5000

CPU: 1 PID: 5000 Comm: syz-executor148 Not tainted 6.4.0-rc7-syzkaller-00041-ge660abd551f1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
 print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
 print_report mm/kasan/report.c:462 [inline]
 kasan_report+0x11c/0x130 mm/kasan/report.c:572
 f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574
 truncate_dnode+0x229/0x2e0 fs/f2fs/node.c:944
 f2fs_truncate_inode_blocks+0x64b/0xde0 fs/f2fs/node.c:1154
 f2fs_do_truncate_blocks+0x4ac/0xf30 fs/f2fs/file.c:721
 f2fs_truncate_blocks+0x7b/0x300 fs/f2fs/file.c:749
 f2fs_truncate.part.0+0x4a5/0x630 fs/f2fs/file.c:799
 f2fs_truncate include/linux/fs.h:825 [inline]
 f2fs_setattr+0x1738/0x2090 fs/f2fs/file.c:1006
 notify_change+0xb2c/0x1180 fs/attr.c:483
 do_truncate+0x143/0x200 fs/open.c:66
 handle_truncate fs/namei.c:3295 [inline]
 do_open fs/namei.c:3640 [inline]
 path_openat+0x2083/0x2750 fs/namei.c:3791
 do_filp_open+0x1ba/0x410 fs/namei.c:3818
 do_sys_openat2+0x16d/0x4c0 fs/open.c:1356
 do_sys_open fs/open.c:1372 [inline]
 __do_sys_creat fs/open.c:1448 [inline]
 __se_sys_creat fs/open.c:1442 [inline]
 __x64_sys_creat+0xcd/0x120 fs/open.c:1442
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The root cause is, inodeA references inodeB via inodeB's ino, once inodeA
is truncated, it calls truncate_dnode() to truncate data blocks in inodeB's
node page, it traverse mapping data from node->i.i_addr[0] to
node->i.i_addr[ADDRS_PER_BLOCK() - 1], result in out-of-boundary access.

This patch fixes to add sanity check on dnode page in truncate_dnode(),
so that, it can help to avoid triggering such issue, and once it encounters
such issue, it will record newly introduced ERROR_INVALID_NODE_REFERENCE
error into superblock, later fsck can detect such issue and try repairing.

Also, it removes f2fs_truncate_data_blocks() for cleanup due to the
function has only one caller, and uses f2fs_truncate_data_blocks_range()
instead.

## Which versions are affected by CVE-2023-53846?


## How do I fix CVE-2023-53846?

Apply the vendor's patch.

## Is CVE-2023-53846 being exploited?

There is no known exploitation of CVE-2023-53846 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-53846 and fix it if it is affected.

What it is: CVE-2023-53846 is a high-severity use after free vulnerability in Linux, published on 9 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-2023-53846 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-2023-53846/ (Markdown: https://insights.sbomify.com/CVE-2023-53846/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53846
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53846
- OSV: https://osv.dev/vulnerability/CVE-2023-53846

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53846/
Summaries are generated and may contain mistakes; the official description above is the record.