A flaw was found in the Linux kernel's kexec functionality, specifically within the purgatory code used by kexec-tools. This vulnerability occurs when the purgatory code attempts to locate a return address on the stack during a non-kjump kexec operation, but the address is not present. This can lead to a system fault or crash, impacting system availability.

In the Linux kernel, the following vulnerability has been resolved: x86/kexec: Push kjump return address even for non-kjump kexec The version of purgatory code shipped by kexec-tools attempts to look above the top of its stack to find a return address for a kjump, even in a non-kjump kexec. After the commit in Fixes: the word above the stack might not be there, leading to a fault (which is at least now caught by my exception-handling code in kexec). That commit fixed things for the actual kjump path, but no longer "gratuitously" pushes the unused return address to the stack in the non-kjump path. Put that *back* in the non-kjump path, to prevent purgatory from crashing when trying to access it.

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

In the Linux kernel, the following vulnerability has been resolved: x86/kexec: Push kjump return address even for non-kjump kexec The version of purgatory code shipped by kexec-tools attempts to look above the top of its stack to find a return address for a kjump, even in a non-kjump kexec. After the commit in Fixes: the word above the stack might not be there, leading to a fault (which is at least now caught by my exception-handling code in kexec). That commit fixed things for the actual kjump path, but no longer "gratuitously" pushes the unused return address to the stack in the non-kjump path. Put that *back* in the non-kjump path, to prevent purgatory from crashing when trying to access it.