linux-kernel - Re: [PATCH 1/1] selinux: fix double free

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Message-ID: <5bfa5213-7d1b-684a-9e21-488fcbf14b91@redhat.com>
Date:   Wed, 10 Jun 2020 13:00:35 -0700
From:   Tom Rix <trix@...hat.com>
To:     Stephen Smalley <stephen.smalley.work@...il.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Jeffrey Vander Stoep <jeffv@...gle.com>, rgb@...hat.com,
        SElinux list <selinux@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] selinux: fix double free



>> +++ b/security/selinux/ss/services.c
>> @@ -2888,8 +2888,12 @@ int security_get_bools(struct selinux_state *state,
>>         if (*names) {
>>                 for (i = 0; i < *len; i++)
>>                         kfree((*names)[i]);
>> +               kfree(names);
> kfree(*names)?

Yes.

> kfree(*values);
>> +       *len = 0;
>> +       *names = NULL;
>> +       *values = NULL;
>>         goto out;
>>  }
> Wondering if the caller handling ought to be changed too even though
> this should avoid the problem.
>
The poisoning of the returns avoids this.