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24Track

xfs: resample the data fork mapping after cycling ILOCK

Linux kernel · CVE-2026-64600
0 news outlets0 CERTs and agencies1 researchers

Assessment: Track

SSVC decision points: exploitation none, automatable no, technical impact total, deployment high.

What is it?

In the Linux kernel, the following vulnerability has been resolved: xfs: resample the data fork mapping after cycling ILOCK xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode, a data fork mapping, and a cow fork mapping. Unfortunately, these two helpers cycle the ILOCK to grab a transaction, which means that the mappings are stale as soon as we reacquire the ILOCK. Currently we refresh the cow fork mapping by re-calling xfs_find_trim_cow_extent, but we don't refresh the data fork mapping beforehand, which means that the xfs_bmap_trim_cow in that function queries the refcount btree about the wrong physical blocks and returns an inaccurate value in *shared. If *shared is now false, the directio write proceeds with a stale data fork mapping. Fix this by querying the data fork mapping if the sequence counter changes across the ILOCK cycle.

Evidence

Technical advisories (1)
Detailed write-ups from security research teams

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
7.8
EPSS
0.5%
First seen
7 d ago
Status
confirmed

All Linux vulnerabilities