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From:   Stephen Smalley <stephen.smalley.work@gmail.com>
Date:   Wed, 17 Jun 2020 09:58:35 -0400
Message-ID: <CAEjxPJ5uGV-SjKL7v5J=7YYEBOjyHwK625SX8fzCrbatuB=9hg@mail.gmail.com>
Subject: Re: [PATCH] selinux: fix undefined return of cond_evaluate_expr
To:     trix@redhat.com
Cc:     Paul Moore <paul@paul-moore.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 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()?