Affected: Linux

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

fs/ntfs3: validate lcns_follow in log_replay conversion

log_replay() converts DIR_PAGE_ENTRY_32 records into DIR_PAGE_ENTRY records when replaying version 0 restart tables.

During this conversion, the memmove() length is derived directly from the on-disk lcns_follow field:

memmove(&dp->vcn, &dp0->vcn_low, 2 * sizeof(u64) + le32_to_cpu(dp->lcns_follow) * sizeof(u64));

check_rstbl() validates restart table structure, but does not constrain per-entry lcns_follow values relative to the entry size. A malformed filesystem image can provide an oversized lcns_follow value, causing the conversion memmove() to access memory beyond the bounds of the allocated restart table buffer.

The same field is later used to bound iteration over page_lcns[], so validating lcns_follow during conversion also prevents downstream out-of-bounds access from the same malformed metadata.

Compute the maximum valid lcns_follow from the already-validated restart table entry size and reject entries that exceed this bound. Reuse the existing t16/t32 scratch variables already declared in log_replay() to avoid introducing new declarations.

[almaz.alexandrovich@paragon-software.com: fixed the conflicts]