CVE-2025-21818 Information

Description

In the Linux kernel the following vulnerability has been resolved:

x86/xen: fix xen_hypercall_hvm() to not clobber %rbx

xen_hypercall_hvm() which is used when running as a Xen PVH guest at most only once during early boot is clobbering %rbx. Depending on whether the caller relies on %rbx to be preserved across the call or not this clobbering might result in an early crash of the system.

This can be avoided by using an already saved register instead of %rbx.

Reference

https://git.kernel.org/stable/c/23f6f420cd727d641f95478fcf3bbbee41e4e5d6 https://git.kernel.org/stable/c/242f7584da3ad041a9db809d33d27a8be8eccc29 https://git.kernel.org/stable/c/4890a0858c09d96f3234a8f94663de80a7201bc4 https://git.kernel.org/stable/c/522d726824cc570e0b6bf0b3af4d5a826f1b17c5 https://git.kernel.org/stable/c/98a5cfd2320966f40fe049a9855f8787f0126825