linux-cve-announce - CVE-2024-38592: drm/mediatek: Init `ddp_comp` with devm

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Message-ID: <2024061955-CVE-2024-38592-5b29@gregkh>
Date: Wed, 19 Jun 2024 15:45:58 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-38592: drm/mediatek: Init `ddp_comp` with devm_kcalloc()

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

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

drm/mediatek: Init `ddp_comp` with devm_kcalloc()

In the case where `conn_routes` is true we allocate an extra slot in
the `ddp_comp` array but mtk_drm_crtc_create() never seemed to
initialize it in the test case I ran. For me, this caused a later
crash when we looped through the array in mtk_drm_crtc_mode_valid().
This showed up for me when I booted with `slub_debug=FZPUA` which
poisons the memory initially. Without `slub_debug` I couldn't
reproduce, presumably because the later code handles the value being
NULL and in most cases (not guaranteed in all cases) the memory the
allocator returned started out as 0.

It really doesn't hurt to initialize the array with devm_kcalloc()
since the array is small and the overhead of initting a handful of
elements to 0 is small. In general initting memory to zero is a safer
practice and usually it's suggested to only use the non-initting alloc
functions if you really need to.

Let's switch the function to use an allocation function that zeros the
memory. For me, this avoids the crash.

The Linux kernel CVE team has assigned CVE-2024-38592 to this issue.

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

	Issue introduced in 6.7 with commit 01389b324c97 and fixed in 6.8.12 with commit cf69d0af7db9
	Issue introduced in 6.7 with commit 01389b324c97 and fixed in 6.9.3 with commit 9fe2cc3fa44f
	Issue introduced in 6.7 with commit 01389b324c97 and fixed in 6.10-rc1 with commit 01a2c5123e27

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-2024-38592
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/mediatek/mtk_drm_crtc.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/cf69d0af7db917b82aceaa44b7b1b9376609da22
	https://git.kernel.org/stable/c/9fe2cc3fa44f7ad7ba5f29c1a68b2b924c17b9b1
	https://git.kernel.org/stable/c/01a2c5123e27b3c4685bf2fc4c2e879f6e0c7b33