netdev - RE: [PATCH] net: dsa: drop some VLAs in switch.c

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Date:   Wed, 14 Mar 2018 11:24:30 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Salvatore Mesoraca' <s.mesoraca16@...il.com>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Kernel Hardening" <kernel-hardening@...ts.openwall.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Andrew Lunn" <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Kees Cook <keescook@...omium.org>
Subject: RE: [PATCH] net: dsa: drop some VLAs in switch.c

From: Salvatore Mesoraca
> Sent: 13 March 2018 22:01
> 2018-03-13 20:58 GMT+01:00 Vivien Didelot <vivien.didelot@...oirfairelinux.com>:
> > Hi Salvatore,
> 
> Hi Vivien,
> 
> > 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.
> 
> I can rewrite the patch using kmalloc.
> Although, if ds->num_ports will always be less than or equal to 12, it
> should be better to
> just use DSA_MAX_PORTS.

Isn't using DECLARE_BITMAP() completely OTT when the maximum size is less
than the number of bits in a word?

	David