Subject: CVE-2024-40970: Avoid hw_desc array overrun in dw-axi-dmac

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

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

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

Avoid hw_desc array overrun in dw-axi-dmac

I have a use case where nr_buffers = 3 and in which each descriptor is composed by 3
segments, resulting in the DMA channel descs_allocated to be 9. Since axi_desc_put()
handles the hw_desc considering the descs_allocated, this scenario would result in a
kernel panic (hw_desc array will be overrun).

To fix this, the proposal is to add a new member to the axi_dma_desc structure,
where we keep the number of allocated hw_descs (axi_desc_alloc()) and use it in
axi_desc_put() to handle the hw_desc array correctly.

Additionally I propose to remove the axi_chan_start_first_queued() call after completing
the transfer, since it was identified that unbalance can occur (started descriptors can
be interrupted and transfer ignored due to DMA channel not being enabled).

The Linux kernel CVE team has assigned CVE-2024-40970 to this issue.

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

	Fixed in 5.15.162 with commit 7c3bb96a20cd
	Fixed in 6.1.96 with commit dd42570018f5
	Fixed in 6.6.36 with commit e151ae1ee065
	Fixed in 6.9.7 with commit 9004784e8d68
	Fixed in 6.10 with commit 333e11bf47fa

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-2024-40970
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/dma/dw-axi-dmac/dw-axi-dmac-platform.c
	drivers/dma/dw-axi-dmac/dw-axi-dmac.h

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/7c3bb96a20cd8db3b8824b2ff08b6cde4505c7e5
	https://git.kernel.org/stable/c/dd42570018f5962c10f215ad9c21274ed5d3541e
	https://git.kernel.org/stable/c/e151ae1ee065cf4b8ce4394ddb9d9c8df6370c66
	https://git.kernel.org/stable/c/9004784e8d68bcd1ac1376407ba296fa28f04dbe
	https://git.kernel.org/stable/c/333e11bf47fa8d477db90e2900b1ed3c9ae9b697