CVE-2026-90117

Summary

In the Linux kernel, the following vulnerability has been resolved:

ntfs: validate usa_ofs before preserving the update sequence number

When ntfs_mft_record_alloc() reuses a free mft record it reads the old update sequence number straight from the on-disk record:

 usn = *(__le16 *)((u8 *)m + le16_to_cpu(m->usa_ofs));

Here m points into the raw $MFT page-cache folio, which still holds unvalidated, MST-protected bytes: the folio is read by a plain iomap_read_folio() and neither post_read_mst_fixup() nor ntfs_mft_record_check() has run on it (both work on private copies). m->usa_ofs is therefore an untrusted u16, and a corrupted record can put it past the end of the record so the two-byte read lands outside the folio. Reading such a record while creating a file gives, under KASAN:

BUG: KASAN: use-after-free in ntfs_mft_record_alloc+… Read of size 2 at addr … ntfs_mft_record_alloc -> __ntfs_create -> ntfs_create -> path_openat

Only preserve the old update sequence number when usa_ofs is even and in range, mirroring the check ntfs_mft_record_check() already applies; otherwise leave usn zero, which the existing restore below skips.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/ea5a3c30710710c1dc5e483d3313309ec2e868f7
• https://git.kernel.org/stable/c/81684340963da2e898eabb8c1e274433d9375bc6

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