AZL-68468

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

fbcon: fix integer overflow in fbcondoset_font

Fix integer overflow vulnerabilities in fbcondoset_font() where font size calculations could overflow when handling user-controlled font parameters.

The vulnerabilities occur when: 1. CALCFONTSZ(h, pitch, charcount) performs h * pith * charcount multiplication with user-controlled values that can overflow. 2. FONTEXTRA_WORDS * sizeof(int) + size addition can also overflow 3. This results in smaller allocations than expected, leading to buffer overflows during font data copying.

Add explicit overflow checking using checkmuloverflow() and checkaddoverflow() kernel helpers to safety validate all size calculations before allocation.