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

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Date:	Mon, 25 Apr 2016 18:34:57 +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 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...

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