Subject: CVE-2024-35920: media: mediatek: vcodec: adding lock to protect decoder context list

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

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

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

media: mediatek: vcodec: adding lock to protect decoder context list

Add a lock for the ctx_list, to avoid accessing a NULL pointer
within the 'vpu_dec_ipi_handler' function when the ctx_list has
been deleted due to an unexpected behavior on the SCP IP block.

Hardware name: Google juniper sku16 board (DT)
pstate: 20400005 (nzCv daif +PAN -UAO -TCO BTYPE=--)
pc : vpu_dec_ipi_handler+0x58/0x1f8 [mtk_vcodec_dec]
lr : scp_ipi_handler+0xd0/0x194 [mtk_scp]
sp : ffffffc0131dbbd0
x29: ffffffc0131dbbd0 x28: 0000000000000000
x27: ffffff9bb277f348 x26: ffffff9bb242ad00
x25: ffffffd2d440d3b8 x24: ffffffd2a13ff1d4
x23: ffffff9bb7fe85a0 x22: ffffffc0133fbdb0
x21: 0000000000000010 x20: ffffff9b050ea328
x19: ffffffc0131dbc08 x18: 0000000000001000
x17: 0000000000000000 x16: ffffffd2d461c6e0
x15: 0000000000000242 x14: 000000000000018f
x13: 000000000000004d x12: 0000000000000000
x11: 0000000000000001 x10: fffffffffffffff0
x9 : ffffff9bb6e793a8 x8 : 0000000000000000
x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : fffffffffffffff0
x3 : 0000000000000020 x2 : ffffff9bb6e79080
x1 : 0000000000000010 x0 : ffffffc0131dbc08
Call trace:
vpu_dec_ipi_handler+0x58/0x1f8 [mtk_vcodec_dec (HASH:6c3f 2)]
scp_ipi_handler+0xd0/0x194 [mtk_scp (HASH:7046 3)]
mt8183_scp_irq_handler+0x44/0x88 [mtk_scp (HASH:7046 3)]
scp_irq_handler+0x48/0x90 [mtk_scp (HASH:7046 3)]
irq_thread_fn+0x38/0x94
irq_thread+0x100/0x1c0
kthread+0x140/0x1fc
ret_from_fork+0x10/0x30
Code: 54000088 f94ca50a eb14015f 54000060 (f9400108)
---[ end trace ace43ce36cbd5c93 ]---
Kernel panic - not syncing: Oops: Fatal exception
SMP: stopping secondary CPUs
Kernel Offset: 0x12c4000000 from 0xffffffc010000000
PHYS_OFFSET: 0xffffffe580000000
CPU features: 0x08240002,2188200c
Memory Limit: none

The Linux kernel CVE team has assigned CVE-2024-35920 to this issue.

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

	Issue introduced in 6.6 with commit 655b86e52eac and fixed in 6.6.27 with commit 0a2dc707aa42
	Issue introduced in 6.6 with commit 655b86e52eac and fixed in 6.8.6 with commit 23aaf8241210
	Issue introduced in 6.6 with commit 655b86e52eac and fixed in 6.9 with commit 6467cda18c9f

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-2024-35920
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/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c
	drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.c
	drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h
	drivers/media/platform/mediatek/vcodec/decoder/vdec_vpu_if.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/0a2dc707aa42214f9c4827bd57e344e29a0841d6
	https://git.kernel.org/stable/c/23aaf824121055ba81b55f75444355bd83c8eb38
	https://git.kernel.org/stable/c/6467cda18c9f9b5f2f9a0aa1e2861c653e41f382