# CVE-2026-98907: Linux kernel btrfs race condition in sb_write_pointer

Source: https://junglewise.ai/threats/cve-2026-98907-in-the-linux-kernel-the-following-vulnerability-has-been-resolved  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-23. Updated: 2026-10-23  
License: CC BY 4.0 with a link back

CVE-2026-98907 · Severity: info · Published 2026-10-23

The Linux kernel's btrfs file system has a race condition in the sb_write_pointer() function that can occur when reading the superblock while the block device's block size is being changed via the BLKBSZSET ioctl. This race condition could lead to reading stale or inconsistent superblock data, potentially causing file system corruption or data loss during concurrent operations.

Technologies: [Linux kernel](https://junglewise.ai/threats/technologies/x-linux-kernel).

## Quick answers

**Is CVE-2026-98907 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-98907 being exploited in the wild.

**How severe is CVE-2026-98907?** Informational severity, published 23 October 2026.

**Which products and versions are affected?** Linux kernel multiple versions (fix applied across stable branches 4.x through 7.x).

**Is there a fix for CVE-2026-98907?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-98907 attacked?** It is attacked with local access, in an operating system.

**Am I affected by CVE-2026-98907?** Check whether you run Linux kernel at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A race condition exists in btrfs's sb_write_pointer() function, which reads the superblock from the block device page cache using read_cache_page_gfp(). The function lacks synchronization against BLKBSZSET block size changes (a similar issue was previously fixed in commit 3f29d661e568). The fix adds filemap_invalidate_lock()/filemap_invalidate_unlock() calls around the read_cache_page_gfp() operation to serialize reads against block size modifications, preventing the function from accessing invalidated or stale page cache entries.

## Affected products

- Linux Kernel multiple versions (fix applied across stable branches 4.x through 7.x)

## Timeline

- 2026-10-23: disclosed: Public disclosure via NVD and stable kernel tree

## References

- [https://git.kernel.org/stable/c/123b9a545f4d0348e81f558a032bf2a93ee5722f](https://git.kernel.org/stable/c/123b9a545f4d0348e81f558a032bf2a93ee5722f)
- [https://git.kernel.org/stable/c/1a6c92aa7242a04e4349c0ea213dbf703a1c9891](https://git.kernel.org/stable/c/1a6c92aa7242a04e4349c0ea213dbf703a1c9891)

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