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Date:   Mon, 17 Aug 2020 13:25:45 +0200
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH] iproute2: ip maddress: Check multiaddr length

On Fri, Aug 14, 2020 at 08:27:56AM -0700, Stephen Hemminger wrote:
> On Fri, 14 Aug 2020 10:46:26 +0200
> Sascha Hauer <s.hauer@...gutronix.de> wrote:
> 
> > ip maddress add|del takes a MAC address as argument, so insist on
> > getting a length of ETH_ALEN bytes. This makes sure the passed argument
> > is actually a MAC address and especially not an IPv4 address which
> > was previously accepted and silently taken as a MAC address.
> > 
> > While at it, do not print *argv in the error path as this has been
> > modified by ll_addr_a2n() and doesn't contain the full string anymore,
> > which can lead to misleading error messages.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de>
> > ---
> >  ip/ipmaddr.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/ip/ipmaddr.c b/ip/ipmaddr.c
> > index 3400e055..9979ed58 100644
> > --- a/ip/ipmaddr.c
> > +++ b/ip/ipmaddr.c
> > @@ -291,7 +291,7 @@ static int multiaddr_modify(int cmd, int argc, char **argv)
> >  {
> >  	struct ifreq ifr = {};
> >  	int family;
> > -	int fd;
> > +	int fd, len;
> >  
> >  	if (cmd == RTM_NEWADDR)
> >  		cmd = SIOCADDMULTI;
> > @@ -313,9 +313,12 @@ static int multiaddr_modify(int cmd, int argc, char **argv)
> >  				usage();
> >  			if (ifr.ifr_hwaddr.sa_data[0])
> >  				duparg("address", *argv);
> > -			if (ll_addr_a2n(ifr.ifr_hwaddr.sa_data,
> > -					14, *argv) < 0) {
> > -				fprintf(stderr, "Error: \"%s\" is not a legal ll address.\n", *argv);
> > +			len = ll_addr_a2n(ifr.ifr_hwaddr.sa_data, 14, *argv);
> 
> While you are at it, get rid of the hard code 14 here and use sizeof(ifr.ifr_hwaddr.sa_data)?

Ok. I just sent out a v2.

Sascha

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