Subject: CVE-2024-40916: drm/exynos: hdmi: report safe 640x480 mode as a fallback when no EDID found

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

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

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

drm/exynos: hdmi: report safe 640x480 mode as a fallback when no EDID found

When reading EDID fails and driver reports no modes available, the DRM
core adds an artificial 1024x786 mode to the connector. Unfortunately
some variants of the Exynos HDMI (like the one in Exynos4 SoCs) are not
able to drive such mode, so report a safe 640x480 mode instead of nothing
in case of the EDID reading failure.

This fixes the following issue observed on Trats2 board since commit
13d5b040363c ("drm/exynos: do not return negative values from .get_modes()"):

[drm] Exynos DRM: using 11c00000.fimd device for DMA mapping operations
exynos-drm exynos-drm: bound 11c00000.fimd (ops fimd_component_ops)
exynos-drm exynos-drm: bound 12c10000.mixer (ops mixer_component_ops)
exynos-dsi 11c80000.dsi: [drm:samsung_dsim_host_attach] Attached s6e8aa0 device (lanes:4 bpp:24 mode-flags:0x10b)
exynos-drm exynos-drm: bound 11c80000.dsi (ops exynos_dsi_component_ops)
exynos-drm exynos-drm: bound 12d00000.hdmi (ops hdmi_component_ops)
[drm] Initialized exynos 1.1.0 20180330 for exynos-drm on minor 1
exynos-hdmi 12d00000.hdmi: [drm:hdmiphy_enable.part.0] *ERROR* PLL could not reach steady state
panel-samsung-s6e8aa0 11c80000.dsi.0: ID: 0xa2, 0x20, 0x8c
exynos-mixer 12c10000.mixer: timeout waiting for VSYNC
------------[ cut here ]------------
WARNING: CPU: 1 PID: 11 at drivers/gpu/drm/drm_atomic_helper.c:1682 drm_atomic_helper_wait_for_vblanks.part.0+0x2b0/0x2b8
[CRTC:70:crtc-1] vblank wait timed out
Modules linked in:
CPU: 1 PID: 11 Comm: kworker/u16:0 Not tainted 6.9.0-rc5-next-20240424 #14913
Hardware name: Samsung Exynos (Flattened Device Tree)
Workqueue: events_unbound deferred_probe_work_func
Call trace:
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from dump_stack_lvl+0x68/0x88
 dump_stack_lvl from __warn+0x7c/0x1c4
 __warn from warn_slowpath_fmt+0x11c/0x1a8
 warn_slowpath_fmt from drm_atomic_helper_wait_for_vblanks.part.0+0x2b0/0x2b8
 drm_atomic_helper_wait_for_vblanks.part.0 from drm_atomic_helper_commit_tail_rpm+0x7c/0x8c
 drm_atomic_helper_commit_tail_rpm from commit_tail+0x9c/0x184
 commit_tail from drm_atomic_helper_commit+0x168/0x190
 drm_atomic_helper_commit from drm_atomic_commit+0xb4/0xe0
 drm_atomic_commit from drm_client_modeset_commit_atomic+0x23c/0x27c
 drm_client_modeset_commit_atomic from drm_client_modeset_commit_locked+0x60/0x1cc
 drm_client_modeset_commit_locked from drm_client_modeset_commit+0x24/0x40
 drm_client_modeset_commit from __drm_fb_helper_restore_fbdev_mode_unlocked+0x9c/0xc4
 __drm_fb_helper_restore_fbdev_mode_unlocked from drm_fb_helper_set_par+0x2c/0x3c
 drm_fb_helper_set_par from fbcon_init+0x3d8/0x550
 fbcon_init from visual_init+0xc0/0x108
 visual_init from do_bind_con_driver+0x1b8/0x3a4
 do_bind_con_driver from do_take_over_console+0x140/0x1ec
 do_take_over_console from do_fbcon_takeover+0x70/0xd0
 do_fbcon_takeover from fbcon_fb_registered+0x19c/0x1ac
 fbcon_fb_registered from register_framebuffer+0x190/0x21c
 register_framebuffer from __drm_fb_helper_initial_config_and_unlock+0x350/0x574
 __drm_fb_helper_initial_config_and_unlock from exynos_drm_fbdev_client_hotplug+0x6c/0xb0
 exynos_drm_fbdev_client_hotplug from drm_client_register+0x58/0x94
 drm_client_register from exynos_drm_bind+0x160/0x190
 exynos_drm_bind from try_to_bring_up_aggregate_device+0x200/0x2d8
 try_to_bring_up_aggregate_device from __component_add+0xb0/0x170
 __component_add from mixer_probe+0x74/0xcc
 mixer_probe from platform_probe+0x5c/0xb8
 platform_probe from really_probe+0xe0/0x3d8
 really_probe from __driver_probe_device+0x9c/0x1e4
 __driver_probe_device from driver_probe_device+0x30/0xc0
 driver_probe_device from __device_attach_driver+0xa8/0x120
 __device_attach_driver from bus_for_each_drv+0x80/0xcc
 bus_for_each_drv from __device_attach+0xac/0x1fc
 __device_attach from bus_probe_device+0x8c/0x90
 bus_probe_device from deferred_probe_work_func+0x98/0xe0
 deferred_probe_work_func from process_one_work+0x240/0x6d0
 process_one_work from worker_thread+0x1a0/0x3f4
 worker_thread from kthread+0x104/0x138
 kthread from ret_from_fork+0x14/0x28
Exception stack(0xf0895fb0 to 0xf0895ff8)
...
irq event stamp: 82357
hardirqs last  enabled at (82363): [<c01a96e8>] vprintk_emit+0x308/0x33c
hardirqs last disabled at (82368): [<c01a969c>] vprintk_emit+0x2bc/0x33c
softirqs last  enabled at (81614): [<c0101644>] __do_softirq+0x320/0x500
softirqs last disabled at (81609): [<c012dfe0>] __irq_exit_rcu+0x130/0x184
---[ end trace 0000000000000000 ]---
exynos-drm exynos-drm: [drm] *ERROR* flip_done timed out
exynos-drm exynos-drm: [drm] *ERROR* [CRTC:70:crtc-1] commit wait timed out
exynos-drm exynos-drm: [drm] *ERROR* flip_done timed out
exynos-drm exynos-drm: [drm] *ERROR* [CONNECTOR:74:HDMI-A-1] commit wait timed out
exynos-drm exynos-drm: [drm] *ERROR* flip_done timed out
exynos-drm exynos-drm: [drm] *ERROR* [PLANE:56:plane-5] commit wait timed out
exynos-mixer 12c10000.mixer: timeout waiting for VSYNC

The Linux kernel CVE team has assigned CVE-2024-40916 to this issue.

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

	Issue introduced in 5.4.274 with commit 348aa3d47e8b and fixed in 5.4.279 with commit e23f2eaf51ec
	Issue introduced in 5.10.215 with commit a8cb3b072403 and fixed in 5.10.221 with commit 4dfffb50316c
	Issue introduced in 5.15.154 with commit 912c149a52c3 and fixed in 5.15.162 with commit 6d6bb258d886
	Issue introduced in 6.1.84 with commit 8f914db6fe25 and fixed in 6.1.95 with commit c3ca24dfe9a2
	Issue introduced in 6.6.24 with commit b71ae5fb2dd3 and fixed in 6.6.35 with commit 35bcf16b4a28
	Issue introduced in 6.9 with commit 13d5b040363c and fixed in 6.9.6 with commit 510a6c0dfa6e
	Issue introduced in 6.9 with commit 13d5b040363c and fixed in 6.10 with commit 799d4b392417
	Issue introduced in 6.7.12 with commit d930ab0399c3
	Issue introduced in 6.8.3 with commit 1cef1ef376c6

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-2024-40916
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/exynos/exynos_hdmi.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/e23f2eaf51ecb6ab4ceb770e747d50c1db2eb222
	https://git.kernel.org/stable/c/4dfffb50316c761c59386c9b002a10ac6d7bb6c9
	https://git.kernel.org/stable/c/6d6bb258d886e124e5a5328e947b36fdcb3a6028
	https://git.kernel.org/stable/c/c3ca24dfe9a2b3f4e8899af108829b0f4b4b15ec
	https://git.kernel.org/stable/c/35bcf16b4a28c10923ff391d14f6ed0ae471ee5f
	https://git.kernel.org/stable/c/510a6c0dfa6ec61d07a4b64698d8dc60045bd632
	https://git.kernel.org/stable/c/799d4b392417ed6889030a5b2335ccb6dcf030ab