CVE-2026-72196

Summary

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

fs/ntfs3: bound copy_lcns dp->page_lcns[] index in analysis pass

In log_replay()'s analysis pass, after find_dp() returns a valid DIR_PAGE_ENTRY for the (target_attr, target_vcn) tuple, the copy_lcns block walks lrh->lcns_follow further entries:

t16 = le16_to_cpu(lrh->lcns_follow);
for (i = 0; i < t16; i++) {
    size_t j = (size_t)(le64_to_cpu(lrh->target_vcn) -
                        le64_to_cpu(dp->vcn));
    dp->page_lcns[j + i] = lrh->page_lcns[i];
}

find_dp() only validates that target_vcn falls within [dp->vcn, dp->vcn + dp->lcns_follow), i.e., that the FIRST cluster is covered. The walk through the further entries is not bounded against dp->lcns_follow. For a malformed LRH where target_vcn = dp->vcn + dp->lcns_follow - 1 and lrh->lcns_follow > 1, the i > 0 writes overflow the dp's allocated page_lcns[] array.

Add the missing j + lrh->lcns_follow <= dp->lcns_follow guard.

Reproduced under UML+KASAN on mainline 8d90b09e6741 as a slab-out-of-bounds write of size 8 from log_replay+0x68d4 on the mount path.

This is distinct from Pavitra Jha's 2026-05-02 patch ("fs/ntfs3: validate lcns_follow in log_replay conversion", <20260502154252.164586-1-jhapavitra98@gmail.com>) which addresses the separate version-0 dirty-page-table conversion path's memmove(&dp->vcn, …) call. The two fixes are complementary; both should land.

[almaz.alexandrovich@paragon-software.com: clang-formatted the changes, fixed conflicts]

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/9b3d8cc9d54fcded4de51b2b1026ae7182512077
• https://git.kernel.org/stable/c/9b7c28d8c61bdb041936222a09a708531a1c2921
• https://git.kernel.org/stable/c/0f13e823bf86bd1800168ea0bb5bca8b8500a81c
• https://git.kernel.org/stable/c/d240cd98f5f7b65c90f6b2b6abe3232ccdc405ab
• https://git.kernel.org/stable/c/49c86dae0c0ccb8d98ddcdc46987259389c816dd
• https://git.kernel.org/stable/c/5e7b598660cfa8e5af172cf4c65cffc126333307

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