linux-kernel - Re: [PATCH] ima: fix memory leak and invalid memory reference bugs

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Date:	Mon, 05 Dec 2011 14:10:33 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Roberto Sassu <roberto.sassu@...ito.it>
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, srajiv@...ux.vnet.ibm.com,
	jmorris@...ei.org
Subject: Re: [PATCH] ima: fix memory leak and invalid memory reference bugs

On Mon, 2011-12-05 at 16:38 +0100, Roberto Sassu wrote:
> This patch frees the memory of measurements entries that have already
> been inserted in the measurements list and prevent the release when the
> PCR extend operation failed.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@...ito.it>

Thanks for the updated patch. I still need to test it, but it looks
good.  The patch description should probably include an explanation of
how a duplicate measurement is being added.  Something like:

When a new measurement is added to the measurement list, this info is
cached in the iint for performance.  When the inode is flushed from
cache, the associated iint is flushed as well.  Subsequent access to the
inode will cause it to be re-measured and will attempt to unnecessarily
add it to the measurement list.

This patch fixes a memory leak, by freeing the memory of the unnecessary
duplicate measurement, and also fixes an invalid memory reference, by
preventing the freeing of a new valid measurement entry, when the PCR
extend operation fails.

thanks,

Mimi

> ---
>  security/integrity/ima/ima_api.c   |    4 ++--
>  security/integrity/ima/ima_queue.c |   10 ++++++----
>  2 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index 0d50df0..88a2788 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -178,8 +178,8 @@ void ima_store_measurement(struct integrity_iint_cache *iint,
>  	strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
> 
>  	result = ima_store_template(entry, violation, inode);
> -	if (!result)
> +	if (!result || result == -EEXIST)
>  		iint->flags |= IMA_MEASURED;
> -	else
> +	if (result < 0)
>  		kfree(entry);
>  }
> diff --git a/security/integrity/ima/ima_queue.c b/security/integrity/ima/ima_queue.c
> index 8e28f04..0fe41b81 100644
> --- a/security/integrity/ima/ima_queue.c
> +++ b/security/integrity/ima/ima_queue.c
> @@ -94,7 +94,8 @@ static int ima_pcr_extend(const u8 *hash)
> 
>  	result = tpm_pcr_extend(TPM_ANY_NUM, CONFIG_IMA_MEASURE_PCR_IDX, hash);
>  	if (result != 0)
> -		pr_err("IMA: Error Communicating to TPM chip\n");
> +		pr_err("IMA: Error Communicating to TPM chip, result: %d\n",
> +		       result);
>  	return result;
>  }
> 
> @@ -107,13 +108,14 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
>  	u8 digest[IMA_DIGEST_SIZE];
>  	const char *audit_cause = "hash_added";
>  	int audit_info = 1;
> -	int result = 0;
> +	int result = 0, tpmresult = 0;
> 
>  	mutex_lock(&ima_extend_list_mutex);
>  	if (!violation) {
>  		memcpy(digest, entry->digest, sizeof digest);
>  		if (ima_lookup_digest_entry(digest)) {
>  			audit_cause = "hash_exists";
> +			result = -EEXIST;
>  			goto out;
>  		}
>  	}
> @@ -128,8 +130,8 @@ int ima_add_template_entry(struct ima_template_entry *entry, int violation,
>  	if (violation)		/* invalidate pcr */
>  		memset(digest, 0xff, sizeof digest);
> 
> -	result = ima_pcr_extend(digest);
> -	if (result != 0) {
> +	tpmresult = ima_pcr_extend(digest);
> +	if (tpmresult != 0) {
>  		audit_cause = "TPM error";
>  		audit_info = 0;
>  	}


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