linux-kernel - Re: [PATCH v1 1/1] KVM: add missing kvm_put

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Message-ID: <a3c75dcd-f31d-e8cc-3402-e43dbefe382d@redhat.com>
Date:   Tue, 27 Jun 2017 15:57:23 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Al Viro <viro@...IV.linux.org.uk>
Cc:     Claudio Imbrenda <imbrenda@...ux.vnet.ibm.com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        borntraeger@...ibm.com, frankja@...ux.vnet.ibm.com
Subject: Re: [PATCH v1 1/1] KVM: add missing kvm_put_kvm in case of failure



On 27/06/2017 15:50, Al Viro wrote:
>> Queued, thanks.
> It's broken.  Look: once we are past the anon_inode_getfile(), the
> reference we held on kvm is transferred into new struct file.  After
> that point we don't drop kvm - we drop file.  And as long as that
> file is held, it will keep holding what used to be our reference to
> kvm.  Once all references to file are gone, its ->release() will be
> called and that's where kvm reference in it will be dropped.
> 
> IOW, this patch introduces a double-put.

Yup, I've noticed your other reply (hopefully would have noticed during
regression testing).  Thanks Al.

Paolo