CVE-2026-64399: ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

From: Greg Kroah-Hartman <[email protected]>

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

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

ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

The FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the
destination file's data via vfs_clone_file_range() with neither the
share-level KSMBD_TREE_CONN_FLAG_WRITABLE check nor a per-handle
fp->daccess check that the other write-bearing arms carry. A client can
overwrite destination data on a read-only share, or from a handle opened
with only FILE_WRITE_ATTRIBUTES (which still yields an FMODE_WRITE filp).
FILE_WRITE_ATTRIBUTES-only destination handle overwrote the file's data via
the clone. Add both checks, matching the FSCTL_SET_SPARSE permission fix;
require FILE_WRITE_DATA since this writes data.

The Linux kernel CVE team has assigned CVE-2026-64399 to this issue.


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

	Fixed in 6.1.178 with commit bf460ad5958d506492de4524a656439da3f99c51
	Fixed in 6.6.145 with commit 620d133d469295ee7c017ca6aafac335f65c4a5a
	Fixed in 6.12.96 with commit 9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6
	Fixed in 6.18.39 with commit baae7b39673ec21073a25e3d14f8feaada01d5df
	Fixed in 7.1.4 with commit c917e4522d251071dde9871b9142d8ea1186ebfe
	Fixed in 7.2-rc1 with commit 388e4139db27a9e3612c9d356b826f5b1ff6a9e3

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-2026-64399
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/smb/server/smb2pdu.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/bf460ad5958d506492de4524a656439da3f99c51
	https://git.kernel.org/stable/c/620d133d469295ee7c017ca6aafac335f65c4a5a
	https://git.kernel.org/stable/c/9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6
	https://git.kernel.org/stable/c/baae7b39673ec21073a25e3d14f8feaada01d5df
	https://git.kernel.org/stable/c/c917e4522d251071dde9871b9142d8ea1186ebfe
	https://git.kernel.org/stable/c/388e4139db27a9e3612c9d356b826f5b1ff6a9e3