CVE-2026-89823: drm: fix race between partial drm_dev_register() failure and ioctl

CVE-2026-89823: drm: fix race between partial drm_dev_register() failure and ioctl

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

drm: fix race between partial drm_dev_register() failure and ioctl

If drm_dev_register() fails after registering a minor (e.g. render minor
registered, primary minor fails), userspace could have opened the first
minor and entered a drm_dev_enter() critical section. Since the
unplugged flag was never set, the ioctl proceeds while the error path
tears down device resources.

Fix this by introducing drm_dev_synchronize_unplug(), which sets the
unplugged flag and waits for the SRCU barrier, ensuring all in-flight
drm_dev_enter() critical sections complete before cleanup proceeds; call
it on the error path of drm_dev_register().

The Linux kernel CVE team has assigned CVE-2026-89823 to this issue.


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

	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 5.10.270 with commit 26d9162213952927cd59c0d94b7e0e992b347bec
	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 5.15.221 with commit 24d28d15c0f7f7d4a1c229f8730314f0f8758810
	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 6.1.188 with commit 6729990df9e70623bf53f855b521ae71ca9cb278
	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 6.6.157 with commit a0a7e2e177f2f18b9e7318a4c64ac44efd9ef22c
	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 6.12.110 with commit 19dbfe4d586aecfed121cb3fa62281761d9d341f
	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 6.18.51 with commit 79d09cfe90304ff4f195e47d569800f5e0f8b854
	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 7.2.5 with commit 2d1215a72159d00001e08dee162e27718934bee9
	Issue introduced in 4.18 with commit bee330f3d67273a68dcb99f59480d59553c008b2 and fixed in 7.3-rc1 with commit eb197f7d60f00d0f5b1b3505dfc86a7e36045a3e

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-2026-89823
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:
	drivers/gpu/drm/drm_drv.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/26d9162213952927cd59c0d94b7e0e992b347bec
	https://git.kernel.org/stable/c/24d28d15c0f7f7d4a1c229f8730314f0f8758810
	https://git.kernel.org/stable/c/6729990df9e70623bf53f855b521ae71ca9cb278
	https://git.kernel.org/stable/c/a0a7e2e177f2f18b9e7318a4c64ac44efd9ef22c
	https://git.kernel.org/stable/c/19dbfe4d586aecfed121cb3fa62281761d9d341f
	https://git.kernel.org/stable/c/79d09cfe90304ff4f195e47d569800f5e0f8b854
	https://git.kernel.org/stable/c/2d1215a72159d00001e08dee162e27718934bee9
	https://git.kernel.org/stable/c/eb197f7d60f00d0f5b1b3505dfc86a7e36045a3e