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

Overview

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", [email protected]) which addresses the separate version-0 dirty-page-table conversion path's memmove(&dp->vcn, ...) call. The two fixes are complementary; both should land.

[[email protected]: clang-formatted the changes, fixed conflicts]

Affected

• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 9b3d8cc9d54fcded4de51b2b1026ae7182512077
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 9b7c28d8c61bdb041936222a09a708531a1c2921
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 0f13e823bf86bd1800168ea0bb5bca8b8500a81c
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < d240cd98f5f7b65c90f6b2b6abe3232ccdc405ab
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 49c86dae0c0ccb8d98ddcdc46987259389c816dd
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 5e7b598660cfa8e5af172cf4c65cffc126333307
• Linux 5.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.