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Re: [Qemu-devel] [PATCH] ps2: fix PS2Queue counter field type
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH] ps2: fix PS2Queue counter field type |
Date: |
Wed, 15 Nov 2017 13:30:35 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
* Paolo Bonzini (address@hidden) wrote:
> On 15/11/2017 13:51, Daniel P. Berrange wrote:
> > If you're concerned that someone is tampering with QEMU state
> > in transit during migration, then you're going to end up playing
> > whack-a-mole across the entire QEMU codebase IMHO. The answer
> > to the problem of tampering is to have encryption of the
> > migration data stream between both QEMU's. Thus QEMU on the
> > target merely has to trust QEMU on the source. If QEMU on the
> > source is itself compromised you've already lost and migration
> > won't make life any worse.
> >
>
> This is not entirely true. A lot of such cases were fixed in the past,
> especially when they could cause out-of-bounds access. Someone could
> provide a bad migration stream (e.g. as a fake bug report!), so
> migration data should not be considered trusted.
There's probably others to be honest; it's not something we've
traditionally been careful of.
> However, PJP's patch breaks migration by changing a 4-byte field to
> 1-byte. The correct fix is to range-check the fields in
> ps2_common_post_load.
Agreed.
Dave
> Thanks,
>
> Paolo
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK