linux-kernel - Re: [PATCH 2/3] KVM: Check validity of offset+length of gfn_to_pfn

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Date: Wed, 20 Mar 2024 08:20:44 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzbot+106a4f72b0474e1d1b33@...kaller.appspotmail.com, Paul Durrant
	 <paul@....org>
Subject: Re: [PATCH 2/3] KVM: Check validity of offset+length of
 gfn_to_pfn_cache prior to activation

On Tue, 2024-03-19 at 17:15 -0700, Sean Christopherson wrote:
> When activating a gfn_to_pfn_cache, verify that the offset+length is sane
> and usable before marking the cache active.  Letting __kvm_gpc_refresh()
> detect the problem results in a cache being marked active without setting
> the GPA (or any other fields), which in turn results in KVM trying to
> refresh a cache with INVALID_GPA.
> 
> Attempting to refresh a cache with INVALID_GPA isn't functionally
> problematic, but it runs afoul of the sanity check that exactly one of
> GPA or userspace HVA is valid, i.e. that a cache is either GPA-based or
> HVA-based.
> 
> Reported-by: syzbot+106a4f72b0474e1d1b33@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/all/0000000000005fa5cc0613f1cebd@google.com
> Fixes: 721f5b0dda78 ("KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA")

Reviewed-by: David Woodhouse <dwmw@...zon.co.uk>


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