Subject: CVE-2022-48898: drm/msm/dp: do not complete dp_aux_cmd_fifo_tx() if irq is not for aux transfer

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

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

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

drm/msm/dp: do not complete dp_aux_cmd_fifo_tx() if irq is not for aux transfer

There are 3 possible interrupt sources are handled by DP controller,
HPDstatus, Controller state changes and Aux read/write transaction.
At every irq, DP controller have to check isr status of every interrupt
sources and service the interrupt if its isr status bits shows interrupts
are pending. There is potential race condition may happen at current aux
isr handler implementation since it is always complete dp_aux_cmd_fifo_tx()
even irq is not for aux read or write transaction. This may cause aux read
transaction return premature if host aux data read is in the middle of
waiting for sink to complete transferring data to host while irq happen.
This will cause host's receiving buffer contains unexpected data. This
patch fixes this problem by checking aux isr and return immediately at
aux isr handler if there are no any isr status bits set.

Current there is a bug report regrading eDP edid corruption happen during
system booting up. After lengthy debugging to found that VIDEO_READY
interrupt was continuously firing during system booting up which cause
dp_aux_isr() to complete dp_aux_cmd_fifo_tx() prematurely to retrieve data
from aux hardware buffer which is not yet contains complete data transfer
from sink. This cause edid corruption.

Follows are the signature at kernel logs when problem happen,
EDID has corrupt header
panel-simple-dp-aux aux-aea0000.edp: Couldn't identify panel via EDID

Changes in v2:
-- do complete if (ret == IRQ_HANDLED) ay dp-aux_isr()
-- add more commit text

Changes in v3:
-- add Stephen suggested
-- dp_aux_isr() return IRQ_XXX back to caller
-- dp_ctrl_isr() return IRQ_XXX back to caller

Changes in v4:
-- split into two patches

Changes in v5:
-- delete empty line between tags

Changes in v6:
-- remove extra "that" and fixed line more than 75 char at commit text

Patchwork: https://patchwork.freedesktop.org/patch/516121/

The Linux kernel CVE team has assigned CVE-2022-48898 to this issue.

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

	Issue introduced in 5.10 with commit c943b4948b58 and fixed in 5.10.164 with commit 785607e5e6fb
	Issue introduced in 5.10 with commit c943b4948b58 and fixed in 5.15.89 with commit 984ad875db80
	Issue introduced in 5.10 with commit c943b4948b58 and fixed in 6.1.7 with commit b7dcbca46db3
	Issue introduced in 5.10 with commit c943b4948b58 and fixed in 6.2 with commit 1cba0d150fa1

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-2022-48898
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/msm/dp/dp_aux.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/785607e5e6fb52caf141e4580de40405565f04f1
	https://git.kernel.org/stable/c/984ad875db804948c86ca9e1c2e784ae8252715a
	https://git.kernel.org/stable/c/b7dcbca46db3c77fdb02c2a9d6239e5aa3b06a59
	https://git.kernel.org/stable/c/1cba0d150fa102439114a91b3e215909efc9f169