netdev - Re: [PATCH iproute2] ip maddr: fix filtering by device

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Message-ID: <20171019090658.GA21378@orbyte.nwl.cc>
Date:   Thu, 19 Oct 2017 11:06:58 +0200
From:   Phil Sutter <phil@....cc>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        netdev@...r.kernel.org, Petr Vorel <pvorel@...e.cz>
Subject: Re: [PATCH iproute2] ip maddr: fix filtering by device

On Thu, Oct 19, 2017 at 10:21:08AM +0200, Michal Kubecek wrote:
> Commit 530903dd9003 ("ip: fix igmp parsing when iface is long") uses
> variable len to keep trailing colon from interface name comparison.  This
> variable is local to loop body but we set it in one pass and use it in
> following one(s) so that we are actually using (pseudo)random length for
> comparison. This became apparent since commit b48a1161f5f9 ("ipmaddr: Avoid
> accessing uninitialized data") always initializes len to zero so that the
> name comparison is always true. As a result, "ip maddr show dev eth0" shows
> IPv4 multicast addresses for all interfaces.
> 
> Instead of keeping the length, let's simply replace the trailing colon with
> a null byte. The bonus is that we get correct interface name in ma.name.
> 
> Fixes: 530903dd9003 ("ip: fix igmp parsing when iface is long")
> Signed-off-by: Michal Kubecek <mkubecek@...e.cz>

Acked-by: Phil Sutter <phil@....cc>