CVE-2025-68296

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

drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup

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.