Re: [PATCH] [RFC] net: dsa: mv88e6xxx: Pre-initialize err in mv88e6xxx_port_bridge_join()

[Vivien Didelot <vivien.didelot@savoirfairelinux.com>]

Hi Geert,

Geert Uytterhoeven <geert@linux-m68k.org> writes:

> On Mon, Apr 25, 2016 at 5:03 PM, Vivien Didelot
> <vivien.didelot@savoirfairelinux.com> wrote:
>> Geert Uytterhoeven <geert@linux-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@linux-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.

Thanks,

        Vivien