Subject: CVE-2024-36895: usb: gadget: uvc: use correct buffer size when parsing configfs lists

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

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

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

usb: gadget: uvc: use correct buffer size when parsing configfs lists

This commit fixes uvc gadget support on 32-bit platforms.

Commit 0df28607c5cb ("usb: gadget: uvc: Generalise helper functions for
reuse") introduced a helper function __uvcg_iter_item_entries() to aid
with parsing lists of items on configfs attributes stores. This function
is a generalization of another very similar function, which used a
stack-allocated temporary buffer of fixed size for each item in the list
and used the sizeof() operator to check for potential buffer overruns.
The new function was changed to allocate the now variably sized temp
buffer on heap, but wasn't properly updated to also check for max buffer
size using the computed size instead of sizeof() operator.

As a result, the maximum item size was 7 (plus null terminator) on
64-bit platforms, and 3 on 32-bit ones. While 7 is accidentally just
barely enough, 3 is definitely too small for some of UVC configfs
attributes. For example, dwFrameInteval, specified in 100ns units,
usually has 6-digit item values, e.g. 166666 for 60fps.

The Linux kernel CVE team has assigned CVE-2024-36895 to this issue.

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

	Issue introduced in 6.3 with commit 0df28607c5cb and fixed in 6.6.31 with commit 7a54e5052bde
	Issue introduced in 6.3 with commit 0df28607c5cb and fixed in 6.8.10 with commit a422089ce42c
	Issue introduced in 6.3 with commit 0df28607c5cb and fixed in 6.9 with commit 650ae71c8074

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-2024-36895
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/usb/gadget/function/uvc_configfs.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/7a54e5052bde582fd0e7677334fe7a5be92e242c
	https://git.kernel.org/stable/c/a422089ce42ced73713e5032aad29a9a7cbe9528
	https://git.kernel.org/stable/c/650ae71c80749fc7cb8858c8049f532eaec64410