Date: Sat, 5 May 2018 11:22:20 -0700 From: Kees Cook <keescook@...omium.org> To: Andrew Lunn <andrew@...n.ch> Cc: Salvatore Mesoraca <s.mesoraca16@...il.com>, Florian Fainelli <f.fainelli@...il.com>, Vivien Didelot <vivien.didelot@...oirfairelinux.com>, LKML <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Network Development <netdev@...r.kernel.org>, "David S. Miller" <davem@...emloft.net> Subject: Re: [PATCH] net: dsa: drop some VLAs in switch.c On Sat, May 5, 2018 at 8:39 AM, Andrew Lunn <andrew@...n.ch> wrote: > On Sat, May 05, 2018 at 12:36:36PM +0200, Salvatore Mesoraca wrote: >> 2018-03-13 21:06 GMT+01:00 Florian Fainelli <f.fainelli@...il.com>: >> > 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 by using DSA_MAX_PORTS instead of ds->num_ports. >> >>> >> >>>  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. >> >> Hi Florian, >> >> Should I consider this patch still NAKed or not? >> Should I resend the patch with some modifications? > > Hi Salvatore > > We have been removing all uses of DSA_MAX_PORTS. I don't particularly > like arbitrary limits on how many ports a switch can have, or how many > switches a board can have. > > So i would prefer to not use DSA_MAX_PORTS here. > > You could make the bitmap part of the dsa_switch structure. This is > allocated by dsa_switch_alloc() and is passed the number of ports. > Doing the allocation there means you don't need to worry about it > failing in dsa_switch_mdb_add() or dsa_switch_vlan_add(). Are dsa_switch_mdb_add() and dsa_switch_vlan_add() guaranteed to be single-threaded? -Kees -- Kees Cook Pixel Security
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