CVE-2026-64600

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 dont 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 Software

References

• 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
• http://www.openwall.com/lists/oss-security/2026/07/22/14
• http://www.openwall.com/lists/oss-security/2026/07/22/18
• http://www.openwall.com/lists/oss-security/2026/07/22/19
• http://www.openwall.com/lists/oss-security/2026/07/31/3
• http://www.openwall.com/lists/oss-security/2026/08/03/4
• http://www.openwall.com/lists/oss-security/2026/08/03/8