CVE-2026-72478 — fs/ntfs3: add bounds check to run_get_highest_vcn()

Affected: Linux

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

fs/ntfs3: add bounds check to run_get_highest_vcn()

run_get_highest_vcn() parses a packed NTFS mapping-pairs buffer without any length bound, relying solely on a 0x00 terminator to stop. A crafted $LogFile UpdateMappingPairs record whose embedded attribute contains mapping-pairs runs without a terminator causes the function to read past the slab allocation, triggering a KASAN slab-out-of-bounds read on mount.

The sibling function run_unpack() received an analogous bounds-check in commit b62567bca474 ("ntfs3: add buffer boundary checks to run_unpack()"), but run_get_highest_vcn() was missed.

Take a run_buf_size parameter and reject any run header whose payload would extend past the buffer end, mirroring the pattern used by run_unpack(). The caller in fslog.c passes the remaining attribute bytes after the mapping-pairs offset.

KASAN report (on mainline v7.1 merge window HEAD):

BUG: KASAN: slab-out-of-bounds in run_get_highest_vcn+0x3c0/0x410 Read of size 1 at addr ffff88800e2d5400 by task mount/72 Call Trace: run_get_highest_vcn+0x3c0/0x410 do_action.isra.0+0x3ba8/0x7b50 log_replay+0x9ddd/0x10200 ntfs_loadlog_and_replay+0x4ad/0x610 ntfs_fill_super+0x214a/0x4540

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CVE-2026-72478 — fs/ntfs3: add bounds check to run_get_highest_vcn()