CVE-2026-53402

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

fbdev: fbcon: fix out-of-bounds read in err_out of fbcon_do_set_font()

When fbcon_do_set_font() fails (e.g., due to a memory allocation failure

inside vc_resize() under heavy memory pressure), it jumps to the `err_out`

label to roll back the console state. However, the current rollback logic

forgets to restore the `hi_font` state, leading to a severe state machine

corruption.

Earlier in the function, `set_vc_hi_font()` might be called to change

`vc->vc_hi_font_mask` and mutate the screen buffer. If `vc_resize()`

subsequently fails, the `err_out` path restores `vc_font.charcount`

but entirely skips rolling back the `vc_hi_font_mask` and the screen

buffer.

This mismatch leaves the terminal in a desynchronized state. Because

`vc_hi_font_mask` remains set, the VT subsystem will still accept

character indices greater than 255 from userspace and write them to the

screen buffer. Subsequent rendering calls (e.g., `fbcon_putcs()`) will

then use these inflated indices to access the reverted, 256-character

font array, leading to a deterministic out-of-bounds read and potential

kernel memory disclosure.

Fix this by adding the missing rollback logic for the `hi_font` mask

and screen buffer in the error path.