linux-kernel - Re: [PATCH] tpm: fix WARNING: lock held when returning to user space

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Message-ID: <20191211180045.GN4516@linux.intel.com>
Date:   Wed, 11 Dec 2019 20:00:45 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Tadeusz Struk <tadeusz.struk@...el.com>
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, jgg@...pe.ca, mingo@...hat.com,
        jeffrin@...agiritech.edu.in, linux-integrity@...r.kernel.org,
        will@...nel.org, peterhuewe@....de
Subject: Re: [PATCH] tpm: fix WARNING: lock held when returning to user space

On Wed, Dec 11, 2019 at 07:52:02PM +0200, Jarkko Sakkinen wrote:
> On Tue, Dec 10, 2019 at 01:17:51PM -0800, Tadeusz Struk wrote:
> > When an application sends TPM commands in NONBLOCKING mode
> > the driver holds chip->tpm_mutex returning from write(),
> > which triggers WARNING: lock held when returning to user space!
> > To silence this warning the driver needs to release the mutex
> > and acquire it again in tpm_dev_async_work() before sending
> > the command.
> 
> This commit message is nonsense ATM. The code leaves locks held,
> which is unacceptable.
> 
> Silencing warnings is worst possible rationale for a code change
> that I can think of starting from the fact that is straight out
> wrong and malicious.

The code change, however, seems to be doing the right thing.

Please bundle it with the test and fix the commit message
appropriately.

/Jarkko