linux-kernel - Re: [PATCH 1/3] netfilter: nf_tables: avoid uninitialized variable warning

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Message-ID: <20160930182006.GA1767@salvia>
Date:   Fri, 30 Sep 2016 20:21:29 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Patrick McHardy <kaber@...sh.net>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        "David S. Miller" <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] netfilter: nf_tables: avoid uninitialized variable
 warning

On Fri, Sep 30, 2016 at 07:47:49PM +0200, Pablo Neira Ayuso wrote:
> On Fri, Sep 30, 2016 at 06:05:34PM +0200, Arnd Bergmann wrote:
> > The newly added nft_range_eval() function handles the two possible
> > nft range operations, but as the compiler warning points out,
> > any unexpected value would lead to the 'mismatch' variable being
> > used without being initialized:
> > 
> > net/netfilter/nft_range.c: In function 'nft_range_eval':
> > net/netfilter/nft_range.c:45:5: error: 'mismatch' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> > 
> > This can be trivially avoided by added a 'default:' clause.
> 
> Applied this patch, I took Aaron's and Pai's patches instead.

Looking at this again, I know uninitialized_var() has been discussed
as not nice since it can hide bugs behind. But if I fix the existing
code to validate priv->op from _init() (this is currently broken), we
can probably use this so save extra code in the packet path for a case
that is not going to happen.

Let me know, thanks!