linux-kernel - Re: [PATCH] net: dsa: drop some VLAs in switch.c

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Message-ID: <b948ef55-8b16-fee4-b22f-4c6d09fea0cf@gmail.com>
Date:   Tue, 13 Mar 2018 13:06:33 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Salvatore Mesoraca <s.mesoraca16@...il.com>,
        linux-kernel@...r.kernel.org
Cc:     kernel-hardening@...ts.openwall.com, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] net: dsa: drop some VLAs in switch.c

On 03/13/2018 12:58 PM, Vivien Didelot wrote:
> Hi Salvatore,
> 
> Salvatore Mesoraca <s.mesoraca16@...il.com> writes:
> 
>> dsa_switch's num_ports is currently fixed to DSA_MAX_PORTS. So we avoid
>> 2 VLAs[1] by using DSA_MAX_PORTS instead of ds->num_ports.
>>
>> [1] https://lkml.org/lkml/2018/3/7/621
>>
>> Signed-off-by: Salvatore Mesoraca <s.mesoraca16@...il.com>
> 
> NAK.
> 
> We are in the process to remove hardcoded limits such as DSA_MAX_PORTS
> and DSA_MAX_SWITCHES, so we have to stick with ds->num_ports.

Then this means that we need to allocate a bitmap from the heap, which
sounds a bit superfluous and could theoretically fail... not sure which
way is better, but bumping the size to DSA_MAX_PORTS definitively does
help people working on enabling -Wvla.
-- 
Florian