linux-kernel - Re: [PATCH] KVM: Add separate helper for putting borrowed reference to kvm

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Message-ID: <e1a4218f-2a70-3de3-1403-dbebf8a8abdf@redhat.com>
Date:   Wed, 27 Nov 2019 17:38:57 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Leonardo Bras <leonardo@...ux.ibm.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paul Mackerras <paulus@...abs.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm-ppc@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: Add separate helper for putting borrowed reference
 to kvm

On 26/11/19 18:53, Leonardo Bras wrote:
> 
> I agree an use-after-free more problem than a memory leak, but I think
> that there is a way to solve this without leaking the memory also.
> 
> One option would be reordering the kvm_put_kvm(), like in this patch:
> https://lkml.org/lkml/2019/11/26/517

It's a tradeoff between "fix one bug" and "mitigate all bugs of that
class", both are good things to do.  Reordering the kvm_put_kvm() fixes
the bug.  kvm_put_kvm_no_destroy() makes all bugs of that kind less
severe, but it doesn't try to fix them.

Paolo



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