CVE-2026-68204: media: vivid: check for vb2_is_busy() when toggling caps

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

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

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

media: vivid: check for vb2_is_busy() when toggling caps

The vivid_update_format_cap/out() functions must only be called if the
capture/output queue are not busy. But for the controls that select
the CROP/COMPOSE/SCALE capability that is not checked.

Only when streaming starts will they be set to 'grabbed' and it is
impossible to change the control, but between REQBUFS and STREAMON you
are still allowed to set these controls. Since vivid_update_format_cap/out
will change the format, this can cause unexpected results.

Besides adding these checks, also add a WARN_ON in
vivid_update_format_cap/out() if the queue is busy.

I'm 90% certain that this is the cause of this syzbot bug:

https://syzkaller.appspot.com/bug?extid=dac8f5eaa46837e97b89

But since we never have reproducers, it is hard to be certain. In any case,
these checks are needed regardless.

The Linux kernel CVE team has assigned CVE-2026-68204 to this issue.


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

	Issue introduced in 3.18 with commit 73c3f48230cda01402ae189b05d56f1f7e0d53c9 and fixed in 6.6.148 with commit a9cd0e8fb0b21faaa71199d9d3feb305c18ff576
	Issue introduced in 3.18 with commit 73c3f48230cda01402ae189b05d56f1f7e0d53c9 and fixed in 6.12.101 with commit abaec6747304581f8d4a9936352fa10e13325f07
	Issue introduced in 3.18 with commit 73c3f48230cda01402ae189b05d56f1f7e0d53c9 and fixed in 6.18.42 with commit 492c97cb50feaa60ccd7792d3d6b904ed8ec61bf
	Issue introduced in 3.18 with commit 73c3f48230cda01402ae189b05d56f1f7e0d53c9 and fixed in 7.1.6 with commit daf2d92669b4a659d805d88d811161c70cd325ee
	Issue introduced in 3.18 with commit 73c3f48230cda01402ae189b05d56f1f7e0d53c9 and fixed in 7.2-rc1 with commit c2d1a2130c93f6d758af58590b86b2254c7a1dec

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-2026-68204
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/media/test-drivers/vivid/vivid-ctrls.c
	drivers/media/test-drivers/vivid/vivid-vid-cap.c
	drivers/media/test-drivers/vivid/vivid-vid-out.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/a9cd0e8fb0b21faaa71199d9d3feb305c18ff576
	https://git.kernel.org/stable/c/abaec6747304581f8d4a9936352fa10e13325f07
	https://git.kernel.org/stable/c/492c97cb50feaa60ccd7792d3d6b904ed8ec61bf
	https://git.kernel.org/stable/c/daf2d92669b4a659d805d88d811161c70cd325ee
	https://git.kernel.org/stable/c/c2d1a2130c93f6d758af58590b86b2254c7a1dec