CVE-2026-53402
HIGHDescription
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.
CVSS v3 vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
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