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.

https://git.kernel.org/stable/c/786a45757dcdf8f2beb9d4a6db605db16c18b2b4

https://git.kernel.org/stable/c/7dba9631faa2ee0785e8c2bf0e3d90a05f26dd8c

https://git.kernel.org/stable/c/b0bd7a850e1f082560959707dbf57b0402071646

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