CVE-2026-68457: ksmbd: use opener credentials for FSCTL mutations

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

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

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

ksmbd: use opener credentials for FSCTL mutations

SET_SPARSE, SET_ZERO_DATA and SET_COMPRESSION operate on an open SMB
handle but call VFS xattr, fallocate or fileattr helpers with the current
ksmbd worker credentials. Those helpers can revalidate inode permissions,
ownership and LSM policy independently of the SMB handle access mask.

Run each operation with the credentials captured in the target file when
the handle was opened. Keep credential handling local to these single-file
FSCTLs rather than applying session credentials to the complete IOCTL
handler, which also contains handle-less and multi-handle operations.

The Linux kernel CVE team has assigned CVE-2026-68457 to this issue.


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

	Fixed in 6.1.178 with commit a8c18434e1f0d9f7989170bdb0490c0160baf065
	Fixed in 6.6.145 with commit 1e112c47ec5dd1942e2d4ca6e8e9b712238e20c2
	Fixed in 6.12.97 with commit fb1cae6302d58414ddf029e3f642711bd30243f7
	Fixed in 6.18.40 with commit e205f3e7e8c31a47cd11efb6cf663a527177e432
	Fixed in 7.1.5 with commit cfb2c6f71d61ed807c9d7a7af331d406f1f31877
	Fixed in 7.2-rc1 with commit c6394bcaf254c5baf9aff43376020be5db6d3316

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-2026-68457
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
	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/a8c18434e1f0d9f7989170bdb0490c0160baf065
	https://git.kernel.org/stable/c/1e112c47ec5dd1942e2d4ca6e8e9b712238e20c2
	https://git.kernel.org/stable/c/fb1cae6302d58414ddf029e3f642711bd30243f7
	https://git.kernel.org/stable/c/e205f3e7e8c31a47cd11efb6cf663a527177e432
	https://git.kernel.org/stable/c/cfb2c6f71d61ed807c9d7a7af331d406f1f31877
	https://git.kernel.org/stable/c/c6394bcaf254c5baf9aff43376020be5db6d3316