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

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Message-Id: <1573582344.17949.67.camel@linux.ibm.com>
Date:   Tue, 12 Nov 2019 13:12:24 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.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 Tue, 2019-11-12 at 09:33 -0800, Lakshmi Ramasubramanian wrote:
> 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.

integrity_kernel_read() returns an error (< 0) or the number of bytes
read.  The while statement ensures that there is more data to read, so
returning 0 is always an error.

Mimi