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Subject: Re: [PATCH] char: tpm: vtpm_proxy: Fix race in init
To:     Jarkko Sakkinen <jarkko@kernel.org>
Cc:     peterhuewe@gmx.de, jgg@ziepe.ca, linux-integrity@vger.kernel.org,
        linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org,
        andrianov@ispras.ru
References: <20210623132226.140341-1-saubhik.mukherjee@gmail.com>
 <20210629172700.yxqnedbayumo5f24@kernel.org>
 <20210629210524.hze6yb23pps3flnv@kernel.org>
From:   Saubhik Mukherjee <saubhik.mukherjee@gmail.com>
Message-ID: <2b7d8d44-791e-284a-a700-5465fbc2c100@gmail.com>
Date:   Wed, 30 Jun 2021 12:54:30 +0530
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On 6/30/21 2:35 AM, Jarkko Sakkinen wrote:
> 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@gmail.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@kernel.org>
> 
> Taking reviewed-by back.
> 
> You're lacking fixes tag. Please re-send with one.
> 
> /Jarkko
> 

Thank you for noticing. I sent the patch containing the Fixes tag in 
reply to your last message. (https://lkml.org/lkml/2021/6/30/104)