netdev - Re: [PATCH net-next v6 03/11] ipv4/route: Allow NULL flowinfo in rt_fill

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Date:   Thu, 20 Jun 2019 21:00:22 +0200
From:   Stefano Brivio <sbrivio@...hat.com>
To:     David Ahern <dsahern@...il.com>
Cc:     David Miller <davem@...emloft.net>, Jianlin Shi <jishi@...hat.com>,
        Wei Wang <weiwan@...gle.com>, Martin KaFai Lau <kafai@...com>,
        Eric Dumazet <edumazet@...gle.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next v6 03/11] ipv4/route: Allow NULL flowinfo in
 rt_fill_info()

On Thu, 20 Jun 2019 07:15:55 -0600
David Ahern <dsahern@...il.com> wrote:

> On 6/19/19 5:59 PM, Stefano Brivio wrote:
> > In the next patch, we're going to use rt_fill_info() to dump exception
> > routes upon RTM_GETROUTE with NLM_F_ROOT, meaning userspace is requesting
> > a dump and not a specific route selection, which in turn implies the input
> > interface is not relevant. Update rt_fill_info() to handle a NULL
> > flowinfo.
> > 
> > Suggested-by: David Ahern <dsahern@...il.com>
> > Signed-off-by: Stefano Brivio <sbrivio@...hat.com>
> > ---
> > v6: New patch
> > 
> >  net/ipv4/route.c | 57 ++++++++++++++++++++++++++----------------------
> >  1 file changed, 31 insertions(+), 26 deletions(-)
> > 
> > diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> > index 66cbe8a7a168..052a80373b1d 100644
> > --- a/net/ipv4/route.c
> > +++ b/net/ipv4/route.c
> > @@ -2699,7 +2699,8 @@ static int rt_fill_info(struct net *net, __be32 dst, __be32 src,
> >  	r->rtm_family	 = AF_INET;
> >  	r->rtm_dst_len	= 32;
> >  	r->rtm_src_len	= 0;
> > -	r->rtm_tos	= fl4->flowi4_tos;
> > +	if (fl4)
> > +		r->rtm_tos	= fl4->flowi4_tos;  
> 
> tracing back to the alloc_skb it does not appear to be initialized to 0,
> so this should be:
> 	r->rtm_tos	= fl4 ? fl4->flowi4_tos : 0;

I guess you're right, but I'm still wondering why I'm not seeing it
with KMSAN. Thanks for catching this, I'll fix it.

-- 
Stefano