linux-kernel - Re: [PATCH v3] ima: drop vla in ima_audit

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Message-Id: <1520805665.3547.7.camel@linux.vnet.ibm.com>
Date:   Sun, 11 Mar 2018 18:01:05 -0400
From:   Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:     Tycho Andersen <tycho@...ho.ws>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v3] ima: drop vla in ima_audit_measurement()

On Thu, 2018-03-08 at 16:08 -0700, Tycho Andersen wrote:
> In keeping with the directive to get rid of VLAs [1], let's drop the VLA
> from ima_audit_measurement(). We need to adjust the return type of
> ima_audit_measurement, because now this function can fail if an allocation
> fails.
> 
> [1]: https://lkml.org/lkml/2018/3/7/621
> 
> v2: just use audit_log_format instead of doing a second allocation
> v3: ignore failures in ima_audit_measurement()
> 
> Signed-off-by: Tycho Andersen <tycho@...ho.ws>

Thanks, this patch has been applied.

Mimi

> ---
>  security/integrity/ima/ima_api.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index 08fe405338e1..2aab9170ef68 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -308,14 +308,17 @@ void ima_audit_measurement(struct integrity_iint_cache *iint,
>  			   const unsigned char *filename)
>  {
>  	struct audit_buffer *ab;
> -	char hash[(iint->ima_hash->length * 2) + 1];
> +	char *hash;
>  	const char *algo_name = hash_algo_name[iint->ima_hash->algo];
> -	char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
>  	int i;
> 
>  	if (iint->flags & IMA_AUDITED)
>  		return;
> 
> +	hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
> +	if (!hash)
> +		return;
> +
>  	for (i = 0; i < iint->ima_hash->length; i++)
>  		hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
>  	hash[i * 2] = '\0';
> @@ -323,18 +326,19 @@ void ima_audit_measurement(struct integrity_iint_cache *iint,
>  	ab = audit_log_start(current->audit_context, GFP_KERNEL,
>  			     AUDIT_INTEGRITY_RULE);
>  	if (!ab)
> -		return;
> +		goto out;
> 
>  	audit_log_format(ab, "file=");
>  	audit_log_untrustedstring(ab, filename);
> -	audit_log_format(ab, " hash=");
> -	snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
> -	audit_log_untrustedstring(ab, algo_hash);
> +	audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);
> 
>  	audit_log_task_info(ab, current);
>  	audit_log_end(ab);
> 
>  	iint->flags |= IMA_AUDITED;
> +out:
> +	kfree(hash);
> +	return;
>  }
> 
>  /*