Medium [CVE-2026-80546] Improve CCA CPRB length and overflow checks

In the Linux kernel, the following vulnerability has been resolved: s390/zcrypt: Improve CCA CPRB length and overflow checks The xcrb_msg_to_type6cprb_msgx() function lacks proper input validation, creating security vulnerabilities: 1.

Integer overflow after CEIL4 alignment: Signed int variables could overflow during 4-byte boundary alignment, causing undersized buffer allocations or incorrect bounds checking. 2.

Missing minimum size validation: The CPRBX structure is copied from userspace without verifying sufficient buffer length. Undersized buffers cause uninitialized memory access when reading structure fields like cprbx.cprb_len and cprbx.domain.

3. Arithmetic overflow in sum calculations: Adding control block and data block sizes could overflow, bypassing size checks and enabling buffer overflows.

Fix by using size_t for length calculations, adding U32_MAX boundary checks after alignment, validating minimum control block size before copying from userspace, and detecting sum calculation overflows.

This vulnerability is due to insufficient input validation, which can lead to integer overflows during memory allocation and arithmetic operations, as well as a lack of minimum size validation for the CPRBX structure.

A local attacker could exploit these issues to cause buffer overflows, potentially leading to arbitrary code execution or information disclosure.