CVE-2026-64395: ksmbd: require source read access for duplicate extents

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

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

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

ksmbd: require source read access for duplicate extents

FSCTL_DUPLICATE_EXTENTS_TO_FILE passes the source file directly to
vfs_clone_file_range() or vfs_copy_file_range() without checking the SMB
access mask granted to the source handle. A handle opened with attribute
access can consequently be used to copy file contents into an
attacker-readable destination.

Require FILE_READ_DATA on the source handle before either VFS operation,
matching other ksmbd data-copy paths.

The Linux kernel CVE team has assigned CVE-2026-64395 to this issue.


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

	Fixed in 6.1.178 with commit 2d2ab6983620c2d60ce7db72133984ca3873b929
	Fixed in 6.6.145 with commit 67bdad9cf01b25030e3bf00bbce6c309319d6663
	Fixed in 6.12.96 with commit b0d4d5cb846a1ddb7aaab9adfb5986e4540e6e5f
	Fixed in 6.18.39 with commit db231af842868268839f9f9619c68cb27830d8be
	Fixed in 7.1.4 with commit a10942af27832c2761d020863a46e79bebe0567d
	Fixed in 7.2-rc1 with commit cedff600f1642aa982178503552f0d007bc829c8

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-2026-64395
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/2d2ab6983620c2d60ce7db72133984ca3873b929
	https://git.kernel.org/stable/c/67bdad9cf01b25030e3bf00bbce6c309319d6663
	https://git.kernel.org/stable/c/b0d4d5cb846a1ddb7aaab9adfb5986e4540e6e5f
	https://git.kernel.org/stable/c/db231af842868268839f9f9619c68cb27830d8be
	https://git.kernel.org/stable/c/a10942af27832c2761d020863a46e79bebe0567d
	https://git.kernel.org/stable/c/cedff600f1642aa982178503552f0d007bc829c8