netdev - Re: [PATCH] [RFC] net: dsa: mv88e6xxx: Pre-initialize err in mv88e6xxx_port_bridge

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Message-ID: <CAMuHMdVfYTx3CCa0GnqmcWHBQPYZZUYZQz1hOOaUjgXFmhVP3w@mail.gmail.com>
Date:	Mon, 25 Apr 2016 19:53:39 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RFC] net: dsa: mv88e6xxx: Pre-initialize err in mv88e6xxx_port_bridge_join()

Hi Vivien,

On Mon, Apr 25, 2016 at 7:31 PM, Vivien Didelot
<vivien.didelot@...oirfairelinux.com> wrote:
> Geert Uytterhoeven <geert@...ux-m68k.org> writes:
>> On Mon, Apr 25, 2016 at 5:03 PM, Vivien Didelot
>> <vivien.didelot@...oirfairelinux.com> wrote:
>>> Geert Uytterhoeven <geert@...ux-m68k.org> writes:
>>>> drivers/net/dsa/mv88e6xxx.c: In function ‘mv88e6xxx_port_bridge_join’:
>>>> drivers/net/dsa/mv88e6xxx.c:2184: warning: ‘err’ may be used uninitialized in this function
>>>
>>> Interesting, I don't have those warnings on 207afda1b5036009...
>>
>> It depends on the compiler version (still using 4.1.2) and options.
>>
>>>> If netdev_notifier_changeupper_info.upper_dev is ever NULL, the bridge
>>>> parameter will be NULL too, and the function will return an
>>>> uninitialized value.
>>>>
>>>> Pre-initialize err to zero to fix this.
>>>>
>>>> Fixes: 207afda1b5036009 ("net: dsa: mv88e6xxx: share the same default FDB")
>>>> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
>>>> ---
>>>> Can this actually happen?
>>>
>>> bridge cannot be NULL here. Also ps->ports[port].bridge_dev is assigned
>>> to it before entering the for loop, so _mv88e6xxx_port_based_vlan_map
>>> will be called at least for this port.
>>
>> But there's no way the compiler can know that...
>
> Or maybe it can in new configurations. Anyway, this fix doesn't hurt,
> with a relevant commit message, I'd ack it.

What would you consider a relevant commit message?

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds