CVE-2026-64600
xfs: resample the data fork mapping after cycling ILOCK
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.
- Affected
- Linux
- CVSS v3.1 CNA
- 7.8 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - EPSS
- 0.47% chance of exploitation in the next 30 days, 39th percentile
- Published
- 2026-07-23
- Updated
- 2026-10-16
Proof-of-concept exploits (9)
- 0xBlackash/CVE-2026-6460021★ · 2026-07-23
- litosmartin/CVE-2026-64600-Refluxfs-PoC4★ · 2026-07-30
- HORKimhab/CVE-2026-646000★ · 2026-08-24
- bha-vin/CVE-2026-64600-Exploit0★ · 2026-07-28
- masrikky/CVE-2026-64600-RefluXFS1★ · 2026-08-08
- 0xSec1/CVE-2026-64600-RefluXFS-PoC0★ · 2026-08-14
- Debajyoti0-0/CVE-2026-646007★ · 2026-07-26
- letsr00t/RefluxFS_CVE-2026-646000★ · 2026-08-04
- k4ntux/COWSlip0★ · 2026-09-26
Security advisories
- https://cdn2.qualys.com/advisory/2026/07/22/RefluXFS.txt
- https://git.kernel.org/stable/c/206c09b04dc5469c7ff14d8aceff2d47c88078d9
- https://git.kernel.org/stable/c/2f4acd0fcd862e22eab45690ec2c08c80b6ef2e7
- https://git.kernel.org/stable/c/44f891bc088958399eec27f7604928694aa35581
- https://git.kernel.org/stable/c/50f0012da1040f69a4e788cd9aed587c9a04983f
- https://git.kernel.org/stable/c/b8c9aa832b52680ee40d6cab0efb081f9a69df05
- https://git.kernel.org/stable/c/dc11be133efca5fe3a2fb02b016dee825cc12f18
- https://git.kernel.org/stable/c/e705d81a7193dd19e69b8e2bad4696d78a4ea075