Re: [PATCH] libelf: Handle PVH kernels lacking ENTRY elfnote

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/10/2020 16:14, Jan Beulich wrote:
> On 15.10.2020 16:50, Jason Andryuk wrote:
>> On Thu, Oct 15, 2020 at 3:00 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>> And why is there no bounds check of ->phys_entry paralleling the
>>> ->virt_entry one?
>> What is the purpose of this checking?  It's sanity checking which is
>> generally good, but what is the harm from failing the checks?  A
>> corrupt kernel can crash itself?  Maybe you could start executing
>> something (the initramfs?) instead of the actual kernel?
> This is at least getting close to a possible security issue.
> Booting a hacked up binary can be a problem afaik.

It's only a security issue if the absence of the check is going to cause
a malfunction outside of guest the guest context.  (e.g. in the
toolstack's elf parser)

There are a functionally infinite ways for a guest kernel to crash
itself early on boot - malforming the ELF header such that the state of
the guest once executing doesn't boot isn't interesting from this point
of view.

~Andrew