From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tomas Bortoli <tomasbortoli@gmail.com>
Subject: Re: [PATCH] KVM: validate userspace input in
 kvm_clear_dirty_log_protect()
Date: Tue, 8 Jan 2019 17:28:05 +0100
Message-ID: <8418f6c8-0fc8-e22c-c39a-bfcaee7471e2@gmail.com>
References: <20190102172937.28741-1-tomasbortoli@gmail.com>
 <99de332c-d4e3-0628-8ad1-982032e67690@redhat.com>
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Cc: linux-kernel@vger.kernel.org, syzkaller@googlegroups.com
To: Paolo Bonzini <pbonzini@redhat.com>, rkrcmar@redhat.com,
        kvm@vger.kernel.org
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Hi Paolo,

On 1/7/19 11:42 PM, Paolo Bonzini wrote:
> On 02/01/19 18:29, Tomas Bortoli wrote:
>>  	n = kvm_dirty_bitmap_bytes(memslot);
>> +
>> +	if (n << 3 < log->num_pages || log->first_page > log->num_pages)
>> +		return -EINVAL;
>> +
> 
> This should be
> 
> 	if (log->first_page > memslot->npages ||
> 	    log->num_pages > memslot->npages - log->first_page)
> 		return -EINVAL;
> 
> i.e. the comparison should check the last page in the range, not the
> number of pages.  In addition, using "n" is unnecessary since we do have
> the memslot.  I'll do the changes myself if you prefer, but an ack would
> be nice.
> 
> 


Yeah, I agree. Thanks for the reply and sure you can do the changes, np :)

Tomas