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

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Message-ID: <20210616185301.GV1096940@ziepe.ca>
Date:   Wed, 16 Jun 2021 15:53:01 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>, kernel@...s.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] tpm: Fix tpmrm reference counting

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/

Jason