# CVE-2025-68261: ext4: add i_data_sem protection in ext4_destroy_inline_data_nolock()

> A race condition in the Linux kernel ext4 filesystem can cause a kernel panic, leading to denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2025
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-72469, BELL-CVE-2025-68261, DEBIAN-CVE-2025-68261, GHSA-q2j6-qrc9-gxpm, ROOT-OS-DEBIAN-11-CVE-2025-68261, ROOT-OS-DEBIAN-12-CVE-2025-68261, ROOT-OS-DEBIAN-13-CVE-2025-68261, ROOT-OS-UBUNTU-2204-CVE-2025-68261, ROOT-OS-UBUNTU-2404-CVE-2025-68261, UBUNTU-CVE-2025-68261

## What is CVE-2025-68261?

CVE-2025-68261 is a high-severity vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

ext4: add i_data_sem protection in ext4_destroy_inline_data_nolock()

Fix a race between inline data destruction and block mapping.

The function ext4_destroy_inline_data_nolock() changes the inode data
layout by clearing EXT4_INODE_INLINE_DATA and setting EXT4_INODE_EXTENTS.
At the same time, another thread may execute ext4_map_blocks(), which
tests EXT4_INODE_EXTENTS to decide whether to call ext4_ext_map_blocks()
or ext4_ind_map_blocks().

Without i_data_sem protection, ext4_ind_map_blocks() may receive inode
with EXT4_INODE_EXTENTS flag and triggering assert.

kernel BUG at fs/ext4/indirect.c:546!
EXT4-fs (loop2): unmounting filesystem.
invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:ext4_ind_map_blocks.cold+0x2b/0x5a fs/ext4/indirect.c:546

Call Trace:
 <TASK>
 ext4_map_blocks+0xb9b/0x16f0 fs/ext4/inode.c:681
 _ext4_get_block+0x242/0x590 fs/ext4/inode.c:822
 ext4_block_write_begin+0x48b/0x12c0 fs/ext4/inode.c:1124
 ext4_write_begin+0x598/0xef0 fs/ext4/inode.c:1255
 ext4_da_write_begin+0x21e/0x9c0 fs/ext4/inode.c:3000
 generic_perform_write+0x259/0x5d0 mm/filemap.c:3846
 ext4_buffered_write_iter+0x15b/0x470 fs/ext4/file.c:285
 ext4_file_write_iter+0x8e0/0x17f0 fs/ext4/file.c:679
 call_write_iter include/linux/fs.h:2271 [inline]
 do_iter_readv_writev+0x212/0x3c0 fs/read_write.c:735
 do_iter_write+0x186/0x710 fs/read_write.c:861
 vfs_iter_write+0x70/0xa0 fs/read_write.c:902
 iter_file_splice_write+0x73b/0xc90 fs/splice.c:685
 do_splice_from fs/splice.c:763 [inline]
 direct_splice_actor+0x10f/0x170 fs/splice.c:950
 splice_direct_to_actor+0x33a/0xa10 fs/splice.c:896
 do_splice_direct+0x1a9/0x280 fs/splice.c:1002
 do_sendfile+0xb13/0x12c0 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0x1cf/0x210 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

## Which versions are affected by CVE-2025-68261?


## How do I fix CVE-2025-68261?

Apply the vendor's patch.

## Is CVE-2025-68261 being exploited?

There is no known exploitation of CVE-2025-68261 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68261 and fix it if it is affected.

What it is: CVE-2025-68261 is a high-severity vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-68261 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-2025-68261/ (Markdown: https://insights.sbomify.com/CVE-2025-68261/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68261
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68261
- OSV: https://osv.dev/vulnerability/CVE-2025-68261

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68261/
Summaries are generated and may contain mistakes; the official description above is the record.