linux-kernel - Re: [RFC 3/5] security: smack: fix memleak in smk_write_rules

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Date:	Sat, 15 Jun 2013 12:54:27 -0700
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Tomasz Stanislawski <t.stanislaws@...sung.com>
CC:	linux-security-module@...r.kernel.org, m.szyprowski@...sung.com,
	kyungmin.park@...sung.com, r.krypa@...sung.com,
	linux-kernel@...r.kernel.org,
	Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [RFC 3/5] security: smack: fix memleak in smk_write_rules_list()

On 6/13/2013 8:29 AM, Tomasz Stanislawski wrote:
> The smack_parsed_rule structure is allocated.  If a rule is successfully
> installed then the last reference to the object is lost.  This patch fixes this
> leak. Moreover smack_parsed_rule is allocated on stack because it no longer
> needed ofter smk_write_rules_list() is finished.
>
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@...sung.com>

It looks like this was introduced with the change-rule support.
Prior to that, the rule passed into smk_set_access() was added
to the rule list if it was new. The change-rule support added a
new structure and missed the fact the rule was already allocated.

The patch needs to be rebased so that it does not depend on the
changes from patches 1 and 2 of the set.


> ---
>  security/smack/smackfs.c |   30 ++++++++++--------------------
>  1 file changed, 10 insertions(+), 20 deletions(-)
>
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index 46f111e..e8c57f3 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -447,7 +447,7 @@ static ssize_t smk_write_rules_list(struct file *file, const char __user *buf,
>  					struct mutex *rule_lock, int format)
>  {
>  	struct smack_known *skp;
> -	struct smack_parsed_rule *rule;
> +	struct smack_parsed_rule rule;
>  	char data[SMK_LOAD2LEN + 1];
>  	int rc = -EINVAL;
>  	int load = 0;
> @@ -475,49 +475,39 @@ static ssize_t smk_write_rules_list(struct file *file, const char __user *buf,
>  		goto out;
>  	}
>  
> -	rule = kzalloc(sizeof(*rule), GFP_KERNEL);
> -	if (rule == NULL) {
> -		rc = -ENOMEM;
> -		goto out;
> -	}
> -
>  	if (format == SMK_LONG_FMT) {
>  		/*
>  		 * Be sure the data string is terminated.
>  		 */
>  		data[count] = '\0';
> -		if (smk_parse_long_rule(data, rule, 1, 0))
> -			goto out_free_rule;
> +		if (smk_parse_long_rule(data, &rule, 1, 0))
> +			goto out;
>  	} else if (format == SMK_CHANGE_FMT) {
>  		data[count] = '\0';
> -		if (smk_parse_long_rule(data, rule, 1, 1))
> -			goto out_free_rule;
> +		if (smk_parse_long_rule(data, &rule, 1, 1))
> +			goto out;
>  	} else {
>  		/*
>  		 * More on the minor hack for backward compatibility
>  		 */
>  		if (count == (SMK_OLOADLEN))
>  			data[SMK_OLOADLEN] = '-';
> -		if (smk_parse_rule(data, rule, 1))
> -			goto out_free_rule;
> +		if (smk_parse_rule(data, &rule, 1))
> +			goto out;
>  	}
>  
>  
>  	if (rule_list == NULL) {
>  		load = 1;
> -		skp = smk_find_entry(rule->smk_subject);
> +		skp = smk_find_entry(rule.smk_subject);
>  		rule_list = &skp->smk_rules;
>  		rule_lock = &skp->smk_rules_lock;
>  	}
>  
> -	rc = smk_set_access(rule, rule_list, rule_lock, load);
> -	if (rc == 0) {
> +	rc = smk_set_access(&rule, rule_list, rule_lock, load);
> +	if (rc == 0)
>  		rc = count;
> -		goto out;
> -	}
>  
> -out_free_rule:
> -	kfree(rule);
>  out:
>  	return rc;
>  }

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