CVE-2026-74595: fscrypt: use the mount idmap for the owner check in fscrypt_ioctl_set_policy()

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

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

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

fscrypt: use the mount idmap for the owner check in fscrypt_ioctl_set_policy()

fscrypt_ioctl_set_policy() calls inode_owner_or_capable() with
&nop_mnt_idmap before allowing an encryption policy to be set, instead
of the idmap of the mount the ioctl was issued on.

fscrypt is used by filesystems that support idmapped mounts (e.g. ext4,
f2fs), so on such a mount this compares the caller's fsuid against the
unmapped on-disk owner rather than the mapped owner: the actual owner
can be wrongly denied with -EACCES and an unrelated caller wrongly
allowed.  Use file_mnt_idmap(filp) instead.

The Linux kernel CVE team has assigned CVE-2026-74595 to this issue.


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

	Issue introduced in 5.12 with commit 14f3db5542e62bcf6fe088a09760ac52d55306c5 and fixed in 6.6.152 with commit 33b7e810ce09955aa02f3b632455cf5e7ac990a9
	Issue introduced in 5.12 with commit 14f3db5542e62bcf6fe088a09760ac52d55306c5 and fixed in 6.12.104 with commit 6a67c460b12315033268dce597546984fe5739e7
	Issue introduced in 5.12 with commit 14f3db5542e62bcf6fe088a09760ac52d55306c5 and fixed in 6.18.45 with commit 653e888a24c87b8bbeab44d7e558a1c1a3641088
	Issue introduced in 5.12 with commit 14f3db5542e62bcf6fe088a09760ac52d55306c5 and fixed in 7.1.9 with commit 98516ba8b817f34e86bdd7a5b7a383cff75c3ddf
	Issue introduced in 5.12 with commit 14f3db5542e62bcf6fe088a09760ac52d55306c5 and fixed in 7.2 with commit cf6c993c0feca7984797e634deba3c80342e199a

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-2026-74595
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/crypto/policy.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/33b7e810ce09955aa02f3b632455cf5e7ac990a9
	https://git.kernel.org/stable/c/6a67c460b12315033268dce597546984fe5739e7
	https://git.kernel.org/stable/c/653e888a24c87b8bbeab44d7e558a1c1a3641088
	https://git.kernel.org/stable/c/98516ba8b817f34e86bdd7a5b7a383cff75c3ddf
	https://git.kernel.org/stable/c/cf6c993c0feca7984797e634deba3c80342e199a