In the Linux kernel, the following vulnerability has been resolved:
ntfs: avoid calling post_write_mst_fixup() for invalid index_block
ntfs_icx_ib_sync_write() calls post_write_mst_fixup() when ntfs_ib_write()
returns an error, intending to restore the buffer after a failed write.
However, ntfs_ib_write() returns an error immediately if
pre_write_mst_fixup() validation fails. The caller,
ntfs_icx_ib_sync_write(), interprets any error as a write failure
requiring rollback. It does not differentiate between I/O errors and
validation failures, and calls post_write_mst_fixup() anyway.
Since post_write_mst_fixup() assumes that the index_block contents is
correct, it doesn't perform the boundary checks, which results in
out-of-bounds memory access.
An attacker can craft a malicious NTFS image with:
- large index_block.usa_ofs offset, pointing outside the ntfs_record
- index_block.usa_count = 0, causing integer underflow
- or index_block.usa_count larger than actual number of sectors in the
ntfs_record, causing out-of-bounds access
KASAN reports describing the memory corruption:
==================================================================
BUG: KASAN: slab-out-of-bounds in post_write_mst_fixup+0x19c/0x1d0
Read of size 2 at addr ffff8881586c9018 by task p/9428
Call Trace:
Unknown