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Message-ID: <0bf3eb18d7f2cf941814926cdd4f4ff61079387b.camel@HansenPartnership.com>
Subject: Re: [PATCH v2] tpm: Rework open/close/shutdown to avoid races
From:   James Bottomley <James.Bottomley@HansenPartnership.com>
To:     Sergey Temerkhanov <s.temerkhanov@gmail.com>,
        Peter Huewe <peterhuewe@gmx.de>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Jerry Snitselaar <jsnitsel@redhat.com>,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Thu, 17 Dec 2020 13:05:03 -0800
In-Reply-To: <e7566e1e48f5be9dca034b4bfb67683b5d3cb88f.camel@HansenPartnership.com>
References: <20201215133801.546207-1-s.temerkhanov@gmail.com>
         <e7566e1e48f5be9dca034b4bfb67683b5d3cb88f.camel@HansenPartnership.com>
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On Tue, 2020-12-15 at 10:51 -0800, James Bottomley wrote:
> On Tue, 2020-12-15 at 16:38 +0300, Sergey Temerkhanov wrote:
> > Avoid race condition at shutdown by shutting downn the TPM 2.0
> > devices synchronously. This eliminates the condition when the
> > shutdown sequence sets chip->ops to NULL leading to the following:
> > 
> > [ 1586.593561][ T8669] tpm2_del_space+0x28/0x73
> > [ 1586.598718][ T8669] tpmrm_release+0x27/0x33wq
> > [ 1586.603774][ T8669] __fput+0x109/0x1d
> > [ 1586.608380][ T8669] task_work_run+0x7c/0x90
> > [ 1586.613414][ T8669] prepare_exit_to_usermode+0xb8/0x128
> > [ 1586.619522][ T8669] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [ 1586.626068][ T8669] RIP: 0033:0x4cb4bb
> 
> An actual bug report would have been helpful.  However, from this
> trace it's easy to deduce that tpm2_del_space() didn't get converted
> to the get/put of the chip ops ... it's still trying to do its own
> half arsed thing with tpm_chip_start() and the mutex.  So isn't a
> much simpler fix simply to convert it as below?  compile tested only,
> but if you can test it out I'll send a proper patch.

I got this booted and running here, so I know it works.  What I still
need to know is does it fix your problem?

James