linux-cve-announce - CVE-2025-71067: ntfs: set dummy blocksize to read boot

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Message-ID: <2026011323-CVE-2025-71067-9c81@gregkh>
Date: Tue, 13 Jan 2026 16:31:25 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-71067: ntfs: set dummy blocksize to read boot_block when mounting

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

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

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

ntfs: set dummy blocksize to read boot_block when mounting

When mounting, sb->s_blocksize is used to read the boot_block without
being defined or validated. Set a dummy blocksize before attempting to
read the boot_block.

The issue can be triggered with the following syz reproducer:

  mkdirat(0xffffffffffffff9c, &(0x7f0000000080)='./file1\x00', 0x0)
  r4 = openat$nullb(0xffffffffffffff9c, &(0x7f0000000040), 0x121403, 0x0)
  ioctl$FS_IOC_SETFLAGS(r4, 0x40081271, &(0x7f0000000980)=0x4000)
  mount(&(0x7f0000000140)=@...lb, &(0x7f0000000040)='./cgroup\x00',
        &(0x7f0000000000)='ntfs3\x00', 0x2208004, 0x0)
  syz_clone(0x88200200, 0x0, 0x0, 0x0, 0x0, 0x0)

Here, the ioctl sets the bdev block size to 16384. During mount,
get_tree_bdev_flags() calls sb_set_blocksize(sb, block_size(bdev)),
but since block_size(bdev) > PAGE_SIZE, sb_set_blocksize() leaves
sb->s_blocksize at zero.

Later, ntfs_init_from_boot() attempts to read the boot_block while
sb->s_blocksize is still zero, which triggers the bug.

[almaz.alexandrovich@...agon-software.com: changed comment style, added
return value handling]

The Linux kernel CVE team has assigned CVE-2025-71067 to this issue.


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

	Fixed in 6.6.120 with commit 44a38eb4f7876513db5a1bccde74de9bc4389d43
	Fixed in 6.12.64 with commit 4fff9a625da958a33191c8553a03283786f9f417
	Fixed in 6.18.3 with commit b3c151fe8f543f1a0b8b5df16ce5d97afa5ec85a
	Fixed in 6.19-rc1 with commit d1693a7d5a38acf6424235a6070bcf5b186a360d

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-2025-71067
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/super.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/44a38eb4f7876513db5a1bccde74de9bc4389d43
	https://git.kernel.org/stable/c/4fff9a625da958a33191c8553a03283786f9f417
	https://git.kernel.org/stable/c/b3c151fe8f543f1a0b8b5df16ce5d97afa5ec85a
	https://git.kernel.org/stable/c/d1693a7d5a38acf6424235a6070bcf5b186a360d