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From: Paul Durrant <xadimgnik@gmail.com>
Message-ID: <db8b8156-07b7-4ee1-9343-9f7862fdf98c@xen.org>
Date: Thu, 21 Mar 2024 11:11:35 +0000
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Subject: Re: [PATCH 2/3] KVM: Check validity of offset+length of
 gfn_to_pfn_cache prior to activation
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To: Sean Christopherson <seanjc@google.com>,
 Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
 syzbot+106a4f72b0474e1d1b33@syzkaller.appspotmail.com,
 David Woodhouse <dwmw2@infradead.org>
References: <20240320001542.3203871-1-seanjc@google.com>
 <20240320001542.3203871-3-seanjc@google.com>
Organization: Xen Project
In-Reply-To: <20240320001542.3203871-3-seanjc@google.com>
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On 20/03/2024 00:15, 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@syzkaller.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")
> Cc: David Woodhouse <dwmw2@infradead.org>
> Cc: Paul Durrant <paul@xen.org>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   virt/kvm/pfncache.c | 16 +++++++++-------
>   1 file changed, 9 insertions(+), 7 deletions(-)
> 

Reviewed-by: Paul Durrant <paul@xen.org>