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From:   Paul Moore <paul@paul-moore.com>
Date:   Wed, 17 Jun 2020 16:51:34 -0400
Message-ID: <CAHC9VhT_mAd8pkboQX1xQpxmYkFvK=HW3pUB8_UzbgnW4+=RjA@mail.gmail.com>
Subject: Re: [PATCH] selinux: fix undefined return of cond_evaluate_expr
To:     trix@redhat.com
Cc:     Stephen Smalley <stephen.smalley.work@gmail.com>,
        Eric Paris <eparis@parisplace.org>,
        Ondrej Mosnacek <omosnace@redhat.com>, weiyongjun1@huawei.com,
        SElinux list <selinux@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Wed, Jun 17, 2020 at 9:58 AM Stephen Smalley
<stephen.smalley.work@gmail.com> wrote:
> On Wed, Jun 17, 2020 at 8:40 AM <trix@redhat.com> wrote:
> >
> > From: Tom Rix <trix@redhat.com>
> >
> > clang static analysis reports an undefined return
> >
> > security/selinux/ss/conditional.c:79:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]
> >         return s[0];
> >         ^~~~~~~~~~~
> >
> > static int cond_evaluate_expr( ...
> > {
> >         u32 i;
> >         int s[COND_EXPR_MAXDEPTH];
> >
> >         for (i = 0; i < expr->len; i++)
> >           ...
> >
> >         return s[0];
> >
> > When expr->len is 0, the loop which sets s[0] never runs.
> >
> > So return -1 if the loop never runs.
> >
> > Signed-off-by: Tom Rix <trix@redhat.com>
>
> Acked-by: Stephen Smalley <stephen.smalley.work@gmail.com>
>
> clang didn't complain about the similar pattern in
> security/selinux/ss/services.c:constraint_expr_eval()?

Related question: I appreciate the work you are doing Tom, can you
share how far along you are testing the SELinux code with clang?  I
ask because it would be nice to roll all of these patches up into one
PR for Linus instead of sending multiple updates.

-- 
paul moore
www.paul-moore.com