CVE-2026-64391: ksmbd: use opener credentials for ADS I/O

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

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

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

ksmbd: use opener credentials for ADS I/O

Alternate data streams are stored as xattrs. Unlike regular file I/O,
their read and write paths therefore call VFS xattr helpers which recheck
inode permissions and LSM policy using the current task credentials.

Run ADS I/O with the credentials captured when the SMB handle was opened.

The Linux kernel CVE team has assigned CVE-2026-64391 to this issue.


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

	Fixed in 6.12.96 with commit a8f5d39971bbad9340d49cd41b0e2da9452a649d
	Fixed in 6.18.39 with commit 2b4592cea214683de0f2ce6f8c22c097fb0ea1ab
	Fixed in 7.1.4 with commit 52a56cf53ec834c44ac1b4d16d585f26613ee5ce
	Fixed in 7.2-rc1 with commit baa5e094886fffa7e6272edcb5e08be5ce28262c

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-2026-64391
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/vfs.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/a8f5d39971bbad9340d49cd41b0e2da9452a649d
	https://git.kernel.org/stable/c/2b4592cea214683de0f2ce6f8c22c097fb0ea1ab
	https://git.kernel.org/stable/c/52a56cf53ec834c44ac1b4d16d585f26613ee5ce
	https://git.kernel.org/stable/c/baa5e094886fffa7e6272edcb5e08be5ce28262c