mirror of https://github.com/torvalds/linux.git
eb76d0f555
Protect vga_switcheroo_client_fb_set() with console lock. Avoids OOB
access in fbcon_remap_all(). Without holding the console lock the call
races with switching outputs.
VGA switcheroo calls fbcon_remap_all() when switching clients. The fbcon
function uses struct fb_info.node, which is set by register_framebuffer().
As the fb-helper code currently sets up VGA switcheroo before registering
the framebuffer, the value of node is -1 and therefore not a legal value.
For example, fbcon uses the value within set_con2fb_map() [1] as an index
into an array.
Moving vga_switcheroo_client_fb_set() after register_framebuffer() can
result in VGA switching that does not switch fbcon correctly.
Therefore move vga_switcheroo_client_fb_set() under fbcon_fb_registered(),
which already holds the console lock. Fbdev calls fbcon_fb_registered()
from within register_framebuffer(). Serializes the helper with VGA
switcheroo's call to fbcon_remap_all().
Although vga_switcheroo_client_fb_set() takes an instance of struct fb_info
as parameter, it really only needs the contained fbcon state. Moving the
call to fbcon initialization is therefore cleaner than before. Only amdgpu,
i915, nouveau and radeon support vga_switcheroo. For all other drivers,
this change does nothing.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://elixir.bootlin.com/linux/v6.17/source/drivers/video/fbdev/core/fbcon.c#L2942 # [1]
Fixes:
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|---|---|---|
| .. | ||
| backlight | ||
| console | ||
| fbdev | ||
| logo | ||
| Kconfig | ||
| Makefile | ||
| aperture.c | ||
| cmdline.c | ||
| display_timing.c | ||
| hdmi.c | ||
| nomodeset.c | ||
| of_display_timing.c | ||
| of_videomode.c | ||
| screen_info_generic.c | ||
| screen_info_pci.c | ||
| sticore.c | ||
| vgastate.c | ||
| videomode.c | ||