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

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Date:   Wed, 13 Nov 2019 08:52:37 +0100
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Patrick Callaghan <patrickc@...ux.ibm.com>
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mimi Zohar <zohar@...ux.ibm.com>
Subject: Re: [PATCH] ima: avoid appraise error for hash calc interrupt

On Mon, Nov 11, 2019 at 02:23:48PM -0500, Patrick Callaghan wrote:
> The integrity_kernel_read() call in ima_calc_file_hash_tfm() can return
> a value of 0 before all bytes of the file are read. A value of 0 would
> normally indicate an EOF. This has been observed if a user process is
> causing a file appraisal and is terminated with a SIGTERM signal. The
> most common occurrence of seeing the problem is if a shutdown or systemd
> reload is initiated while files are being appraised.
> 
> The problem is similar to commit <f5e1040196db> (ima: always return
> negative code for error) that fixed the problem in
> ima_calc_file_hash_atfm().
> 
> Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
> Signed-off-by: Patrick Callaghan <patrickc@...ux.ibm.com>
> ---
>  security/integrity/ima/ima_crypto.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
> index 73044fc..7967a69 100644
> --- a/security/integrity/ima/ima_crypto.c
> +++ b/security/integrity/ima/ima_crypto.c
> @@ -362,8 +362,10 @@ static int ima_calc_file_hash_tfm(struct file *file,
>  			rc = rbuf_len;
>  			break;
>  		}
> -		if (rbuf_len == 0)
> +		if (rbuf_len == 0) {	/* unexpected EOF */
> +			rc = -EINVAL;
>  			break;
> +		}

There's no point in calling crypto_shash_final() on incomplete data, so
setting rc to an error to avoid that seems the right thing to do to me,
so:

Reviewed-by: Sascha Hauer <s.hauer@...gutronix.de>

Sascha

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