Bug 2404104 (CVE-2025-39967)

Summary: CVE-2025-39967 kernel: fbcon: fix integer overflow in fbcon_do_set_font
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-10-15 08:02:21 UTC 
In the Linux kernel, the following vulnerability has been resolved:

fbcon: fix integer overflow in fbcon_do_set_font

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

The vulnerabilities occur when:
1. CALC_FONTSZ(h, pitch, charcount) performs h * pith * charcount
   multiplication with user-controlled values that can overflow.
2. FONT_EXTRA_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 check_mul_overflow() and
check_add_overflow() kernel helpers to safety validate all size
calculations before allocation.
Comment 1 Alexander B 2025-10-16 11:14:01 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025101555-CVE-2025-39967-0fbf@gregkh/T