linux-kernel - Re: [PATCH] ima: avoid appraise error for hash calc interrupt

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Message-ID: <c6a57c24-2f30-f252-0f42-8d748ede65af@linux.microsoft.com>
Date:   Tue, 12 Nov 2019 09:33:34 -0800
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>,
        Patrick Callaghan <patrickc@...ux.ibm.com>,
        linux-integrity@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>
Subject: Re: [PATCH] ima: avoid appraise error for hash calc interrupt

On 11/12/2019 9:14 AM, Mimi Zohar wrote:

> On Mon, 2019-11-11 at 14:29 -0800, Lakshmi Ramasubramanian wrote:
>> On 11/11/19 11:23 AM, Patrick Callaghan wrote:
>>
>>> -		if (rbuf_len == 0)
>>> +		if (rbuf_len == 0) {	/* unexpected EOF */
>>> +			rc = -EINVAL;
>>>    			break;
>>> +		}
>>>    		offset += rbuf_len;
>>
>> Should there be an additional check to validate that (offset + rbuf_len)
>> is less than i_size before calling cypto_shash_update (since rbuf_len is
>> one of the parameters for this call)?
> 
> The "while" statement enforces that.
> 
> Mimi

Yes - but that check happens after the call to crypto_shash_update().

Perhaps integrity_kernel_read() will never return (rbuf_len) that will
  => violate the check in the "while" statement.
  => number of bytes read that is greater than the memory allocated for 
rbuf even in error conditions.

Just making sure.

thanks,
  -lakshmi

> 
>>
>>                  if ((rbuf_len == 0) || (offset + rbuf_len >= i_size)) {
>>                           rc = -EINVAL;
>>                           break;
>>                  }
>>                  offset += rbuf_len;
>>
>>>    	       rc = crypto_shash_update(shash, rbuf, rbuf_len);