linux-kernel - Re: [PATCH] char: tpm: vtpm

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Message-ID: <20210629210524.hze6yb23pps3flnv@kernel.org>
Date:   Wed, 30 Jun 2021 00:05:24 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Saubhik Mukherjee <saubhik.mukherjee@...il.com>
Cc:     peterhuewe@....de, jgg@...pe.ca, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org,
        andrianov@...ras.ru
Subject: Re: [PATCH] char: tpm: vtpm_proxy: Fix race in init

On Tue, Jun 29, 2021 at 08:27:00PM +0300, Jarkko Sakkinen wrote:
> On Wed, Jun 23, 2021 at 06:52:26PM +0530, Saubhik Mukherjee wrote:
> > vtpm_module_init calls vtpmx_init which calls misc_register. The file
> > operations callbacks are registered. So, vtpmx_fops_ioctl can execute in
> > parallel with rest of vtpm_module_init. vtpmx_fops_ioctl calls
> > vtpmx_ioc_new_dev, which calls vtpm_proxy_create_device, which calls
> > vtpm_proxy_work_start, which could read uninitialized workqueue.
> > 
> > To avoid this, create workqueue before vtpmx init.
> > 
> > Found by Linux Driver Verification project (linuxtesting.org).
> > 
> > Signed-off-by: Saubhik Mukherjee <saubhik.mukherjee@...il.com>
> > ---
> >  drivers/char/tpm/tpm_vtpm_proxy.c | 19 +++++++++----------
> >  1 file changed, 9 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
> > index 91c772e38bb5..225dfa026a8f 100644
> > --- a/drivers/char/tpm/tpm_vtpm_proxy.c
> > +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
> > @@ -697,23 +697,22 @@ static int __init vtpm_module_init(void)
> >  {
> >  	int rc;
> >  
> > -	rc = vtpmx_init();
> > -	if (rc) {
> > -		pr_err("couldn't create vtpmx device\n");
> > -		return rc;
> > -	}
> > -
> >  	workqueue = create_workqueue("tpm-vtpm");
> >  	if (!workqueue) {
> >  		pr_err("couldn't create workqueue\n");
> > -		rc = -ENOMEM;
> > -		goto err_vtpmx_cleanup;
> > +		return -ENOMEM;
> > +	}
> > +
> > +	rc = vtpmx_init();
> > +	if (rc) {
> > +		pr_err("couldn't create vtpmx device\n");
> > +		goto err_destroy_workqueue;
> >  	}
> >  
> >  	return 0;
> >  
> > -err_vtpmx_cleanup:
> > -	vtpmx_cleanup();
> > +err_destroy_workqueue:
> > +	destroy_workqueue(workqueue);
> >  
> >  	return rc;
> >  }
> > -- 
> > 2.30.2
> > 
> > 
> 
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

Taking reviewed-by back.

You're lacking fixes tag. Please re-send with one.

/Jarkko