linux-kernel - Re: [PATCH] apparmor: Fix use-after-free in aa_audit_rule

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Message-ID: <83dcacc2-a820-fe63-a1b9-1809e8f14f2f@web.de>
Date:   Sun, 20 Oct 2019 16:16:19 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Navid Emamdoost <navid.emamdoost@...il.com>,
        linux-security-module@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Navid Emamdoost <emamd001@....edu>, Kangjie Lu <kjlu@....edu>,
        Stephen McCamant <smccaman@....edu>,
        James Morris <jmorris@...ei.org>,
        John Johansen <john.johansen@...onical.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Tyler Hicks <tyhicks@...onical.com>
Subject: Re: [PATCH] apparmor: Fix use-after-free in aa_audit_rule_init

> … But after this release the the return statement
> tries to access the label field of the rule which results in
> use-after-free. Before releaseing the rule, copy errNo and return it
> after releasing rule.

Please avoid a duplicate word and a typo in this change description.


…
> +++ b/security/apparmor/audit.c
…
> @@ -197,8 +198,9 @@ int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
>  	rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
>  				     GFP_KERNEL, true, false);
>  	if (IS_ERR(rule->label)) {
> +		err = rule->label;

How do you think about to define the added local variable in this if branch directly?

+		int err = rule->label;

>  		aa_audit_rule_free(rule);
> -		return PTR_ERR(rule->label);
> +		return PTR_ERR(err);
>  	}
>
>  	*vrule = rule;


Regards,
Markus