linux-kernel - Re: [PATCH] ipv6: initialize treq->txhash in cookie_v6

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Message-ID: <1500277896.5566.10.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 17 Jul 2017 00:51:36 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     dvyukov@...gle.com, kcc@...gle.com, edumazet@...gle.com,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] ipv6: initialize treq->txhash in cookie_v6_check()

On Mon, 2017-07-17 at 00:39 -0700, Eric Dumazet wrote:
> On Fri, 2017-07-14 at 18:54 +0200, Alexander Potapenko wrote:
> > KMSAN reported use of uninitialized memory in skb_set_hash_from_sk(),
> > which originated from the TCP request socket created in
> > cookie_v6_check():
> 
> >  ==================================================================
> > 
> > Signed-off-by: Alexander Potapenko <glider@...gle.com>
> > ---
> >  net/ipv6/syncookies.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
> > index 7b75b0620730..b4b354502c6e 100644
> > --- a/net/ipv6/syncookies.c
> > +++ b/net/ipv6/syncookies.c
> > @@ -216,6 +216,7 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
> >  	treq->rcv_isn = ntohl(th->seq) - 1;
> >  	treq->snt_isn = cookie;
> >  	treq->ts_off = 0;
> > +	treq->txhash = 0;
> >  
> >  	/*
> >  	 * We need to lookup the dst_entry to get the correct window size.
> 
> Please use net_tx_rndhash() instead of 0, thanks.
> 
> ( And same fix is needed for IPv4, as Neal mentioned already )

Also please add the following tag.

Fixes: 58d607d3e52f ("tcp: provide skb->hash to synack packets")

Thanks again !