fs/ntfs3: validate lcns_follow in log_replay conversion

Overview

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.

[[email protected]: fixed the conflicts]

Affected

• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < ca343a99806b4fc8e27c48f08be3445c5fcd1445
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < ddfc8683e1a627dbf1b83bacf8961443dd654258
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 57c071e2c4f30b9c6f5aacb6679aab1269fbae99
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 159f694d682e4215b3822ae31ed3a4631628fe55
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 7adb38279812c9c06b0e3fa7382f4d7887f3fa2d
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 32b9f8733feb241627fa5f564b1a99b5cae974c5
• Linux >= b46acd6a6a627d876898e1c84d3f84902264b445 < 6a4c53a2e26a865565bd6a460961e8d6fcb32329
• Linux 5.15

Remediation

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