linux/drivers/video
Michael Kelley 9ff5549b1d video: hyperv_fb: Fix validation of screen resolution
In the WIN10 version of the Synthetic Video protocol with Hyper-V,
Hyper-V reports a list of supported resolutions as part of the protocol
negotiation. The driver calculates the maximum width and height from
the list of resolutions, and uses those maximums to validate any screen
resolution specified in the video= option on the kernel boot line.

This method of validation is incorrect. For example, the list of
supported resolutions could contain 1600x1200 and 1920x1080, both of
which fit in an 8 Mbyte frame buffer.  But calculating the max width
and height yields 1920 and 1200, and 1920x1200 resolution does not fit
in an 8 Mbyte frame buffer.  Unfortunately, this resolution is accepted,
causing a kernel fault when the driver accesses memory outside the
frame buffer.

Instead, validate the specified screen resolution by calculating
its size, and comparing against the frame buffer size.  Delete the
code for calculating the max width and height from the list of
resolutions, since these max values have no use.  Also add the
frame buffer size to the info message to aid in understanding why
a resolution might be rejected.

Fixes: 67e7cdb482 ("video: hyperv: hyperv_fb: Obtain screen resolution from Hyper-V host")
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Acked-by: Helge Deller <deller@gmx.de>
Link: https://lore.kernel.org/r/1642360711-2335-1-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
2022-01-24 14:01:12 +00:00
..
backlight backlight: qcom-wled: Respect enabled-strings in set_brightness 2021-12-22 11:18:46 +00:00
console Linux 5.16-rc5 2021-12-14 10:24:28 +01:00
fbdev video: hyperv_fb: Fix validation of screen resolution 2022-01-24 14:01:12 +00:00
logo .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
display_timing.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
hdmi.c video: fix some kernel-doc markups 2020-11-16 18:23:16 +01:00
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile
of_display_timing.c video: Fix kernel-doc warnings in of_display_timing + of_videomode 2020-11-29 22:42:17 +01:00
of_videomode.c video: Fix kernel-doc warnings in of_display_timing + of_videomode 2020-11-29 22:42:17 +01:00
vgastate.c Video: vgastate: fixed a spacing coding style 2018-10-08 12:57:35 +02:00
videomode.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00