linux-kernel - Re: [PATCH v3] audit: fix a memory leak bug

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Message-ID: <20190422131613.ivnshztep4e772xq@madcap2.tricolour.ca>
Date:   Mon, 22 Apr 2019 09:16:13 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Wenwen Wang <wang6495@....edu>
Cc:     "moderated list:AUDIT SUBSYSTEM" <linux-audit@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] audit: fix a memory leak bug

On 2019-04-19 20:49, Wenwen Wang wrote:
> In audit_rule_change(), audit_data_to_entry() is firstly invoked to
> translate the payload data to the kernel's rule representation. In
> audit_data_to_entry(), depending on the audit field type, an audit tree may
> be created in audit_make_tree(), which eventually invokes kmalloc() to
> allocate the tree.  Since this tree is a temporary tree, it will be then
> freed in the following execution, e.g., audit_add_rule() if the message
> type is AUDIT_ADD_RULE or audit_del_rule() if the message type is
> AUDIT_DEL_RULE. However, if the message type is neither AUDIT_ADD_RULE nor
> AUDIT_DEL_RULE, i.e., the default case of the switch statement, this
> temporary tree is not freed.
> 
> To fix this issue, only allocate the tree when the type is AUDIT_ADD_RULE
> or AUDIT_DEL_RULE.
> 
> Signed-off-by: Wenwen Wang <wang6495@....edu>

Looks good to me.

Reviewed-by: Richard Guy Briggs <rgb@...hat.com>

> ---
>  kernel/auditfilter.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 63f8b3f..3ac71c4 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1114,22 +1114,24 @@ int audit_rule_change(int type, int seq, void *data, size_t datasz)
>  	int err = 0;
>  	struct audit_entry *entry;
>  
> -	entry = audit_data_to_entry(data, datasz);
> -	if (IS_ERR(entry))
> -		return PTR_ERR(entry);
> -
>  	switch (type) {
>  	case AUDIT_ADD_RULE:
> +		entry = audit_data_to_entry(data, datasz);
> +		if (IS_ERR(entry))
> +			return PTR_ERR(entry);
>  		err = audit_add_rule(entry);
>  		audit_log_rule_change("add_rule", &entry->rule, !err);
>  		break;
>  	case AUDIT_DEL_RULE:
> +		entry = audit_data_to_entry(data, datasz);
> +		if (IS_ERR(entry))
> +			return PTR_ERR(entry);
>  		err = audit_del_rule(entry);
>  		audit_log_rule_change("remove_rule", &entry->rule, !err);
>  		break;
>  	default:
> -		err = -EINVAL;
>  		WARN_ON(1);
> +		return -EINVAL;
>  	}
>  
>  	if (err || type == AUDIT_DEL_RULE) {
> -- 
> 2.7.4
> 
> --
> Linux-audit mailing list
> Linux-audit@...hat.com
> https://www.redhat.com/mailman/listinfo/linux-audit

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635

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