CVE-2026-89616: fs/ntfs3: fix info-leak on partial LZNT decompress in ni_read_frame()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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

fs/ntfs3: fix info-leak on partial LZNT decompress in ni_read_frame()

ni_read_frame() decompresses an LZNT $DATA frame into the vmapped target
pages and then trusts decompress_lznt()'s return value:

  unc_size = decompress_lznt(frame_ondisk, ondisk_size, frame_mem,
                             frame_size);
  if ((ssize_t)unc_size < 0)        err = unc_size;
  else if (!unc_size || unc_size > frame_size)  err = -EINVAL;

decompress_lznt() stops as soon as the compressed stream is exhausted
(e.g. a zero chunk header) and returns the number of bytes it actually
wrote, which may be far less than frame_size. The bytes between unc_size
and frame_size are never written. The only memset() that follows zeroes
the region beyond i_valid; when the frame lies entirely within the file's
valid size that memset() does not run, so the gap retains whatever was in
the just-vmapped pages. All pages are then marked uptodate and returned
to userspace, disclosing uninitialized (recently-freed) kernel page
memory. A crafted compressed file whose stream decompresses to only a few
bytes leaks the remainder of every frame on a plain read(2), which is
enough to recover kernel pointers and defeat KASLR.

Zero the [unc_size, frame_size) tail immediately after a successful LZNT
decompress so the remainder reads back as zero.

The Linux kernel CVE team has assigned CVE-2026-89616 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.15 with commit 4342306f0f0d5ff4315a204d315c1b51b914fca5 and fixed in 6.12.109 with commit 0f699ddb290a24b37e1bc9bf1e3c9dbccf564bea
	Issue introduced in 5.15 with commit 4342306f0f0d5ff4315a204d315c1b51b914fca5 and fixed in 6.18.50 with commit 376ee45659a4b943df672ad275c63da00655f929
	Issue introduced in 5.15 with commit 4342306f0f0d5ff4315a204d315c1b51b914fca5 and fixed in 7.2.4 with commit 4a1b39b2e10eb8de86265e80cf2be4396bc1dce4
	Issue introduced in 5.15 with commit 4342306f0f0d5ff4315a204d315c1b51b914fca5 and fixed in 7.3-rc1 with commit 35d1ea92c7d946e2ebdbe36cdb2c969c8704bebd

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-89616
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/ntfs3/frecord.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/0f699ddb290a24b37e1bc9bf1e3c9dbccf564bea
	https://git.kernel.org/stable/c/376ee45659a4b943df672ad275c63da00655f929
	https://git.kernel.org/stable/c/4a1b39b2e10eb8de86265e80cf2be4396bc1dce4
	https://git.kernel.org/stable/c/35d1ea92c7d946e2ebdbe36cdb2c969c8704bebd