Linux Kernel Debug Page Allocation Vulnerability on s390 Architecture Causes Boot Crash

A vulnerability in the Linux kernel on s390 architecture has been identified, where the kernel crashes early during boot when debug page allocation is enabled. This issue arises from large memory mappings on machines with EDAT1/EDAT2, leading to a fatal exception and kernel panic. The vulnerability is present in Linux kernel versions through 6.5.0-rc3.

Impact

The vulnerability causes a kernel panic, disrupting the boot process and leading to a system crash.

Reproduction

The vulnerability can be reproduced by booting a machine with the Linux kernel on s390 architecture, with debug page allocation enabled. This can be done by using the 'debug_pagealloc' kernel command line option. The kernel will crash early in the boot process, displaying a fatal exception and kernel panic.

Remediation

Users can disable the 'debug_pagealloc' kernel command line option to prevent this issue. Alternatively, the vulnerability can be addressed by applying the available patch, which splits large memory mappings into 4k pages when debug page allocation is enabled.