linux-kernel - Re: [PATCH 1/2] tpm: Fix tpmrm reference counting

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Message-ID: <20210617053809.GA4049@axis.com>
Date:   Thu, 17 Jun 2021 07:38:09 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
CC:     Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        kernel <kernel@...s.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        <LinoSanfilippo@....de>
Subject: Re: [PATCH 1/2] tpm: Fix tpmrm reference counting

On Wed, Jun 16, 2021 at 08:53:01PM +0200, Jason Gunthorpe wrote:
> On Tue, Jun 15, 2021 at 11:14:08AM +0200, Vincent Whitchurch wrote:
> > The code added by commit 8979b02aaf1d6de8 ("tpm: Fix reference count to
> > main device") tries to take an extra reference to the main device only
> > for TPM2 by looking at the flags, but the flags are actually not set
> > at the time when tpm_chip_alloc() is called, so no extra reference is
> > ever taken, leading to a use-after-free if the TPM modules are removed
> > when the tpmrm device is in use.
> 
> Please read this
> 
> https://lore.kernel.org/linux-integrity/20210205172528.GP4718@ziepe.ca/

Thank you for the pointer.  I see that Lino already posted your proposal
as a real patch as you requested so I will drop this.

 https://lore.kernel.org/linux-integrity/1613949567-1181-2-git-send-email-LinoSanfilippo@gmx.de/