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Date: Mon, 14 Nov 2016 17:44:27 +0100 From: Hannes Frederic Sowa <hannes@...essinduktion.org> To: "Jason A. Donenfeld" <Jason@...c4.com>, David Ahern <dsa@...ulusnetworks.com>, Netdev <netdev@...r.kernel.org>, WireGuard mailing list <wireguard@...ts.zx2c4.com>, LKML <linux-kernel@...r.kernel.org>, YOSHIFUJI Hideaki <hideaki.yoshifuji@...aclelinux.com> Subject: Re: [PATCH v3] ip6_output: ensure flow saddr actually belongs to device On Mon, Nov 14, 2016, at 00:28, Jason A. Donenfeld wrote: > This puts the IPv6 routing functions in parity with the IPv4 routing > functions. Namely, we now check in v6 that if a flowi6 requests an > saddr, the returned dst actually corresponds to a net device that has > that saddr. This mirrors the v4 logic with __ip_dev_find in > __ip_route_output_key_hash. In the event that the returned dst is not > for a dst with a dev that has the saddr, we return -EINVAL, just like > v4; this makes it easy to use the same error handlers for both cases. > > Signed-off-by: Jason A. Donenfeld <Jason@...c4.com> > Cc: David Ahern <dsa@...ulusnetworks.com> > --- > Changes from v2: > It turns out ipv6_chk_addr already has the device enumeration > logic that we need by simply passing NULL. > > net/ipv6/ip6_output.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c > index 6001e78..b3b5cb6 100644 > --- a/net/ipv6/ip6_output.c > +++ b/net/ipv6/ip6_output.c > @@ -926,6 +926,10 @@ static int ip6_dst_lookup_tail(struct net *net, > const struct sock *sk, > int err; > int flags = 0; > > + if (!ipv6_addr_any(&fl6->saddr) && > + !ipv6_chk_addr(net, &fl6->saddr, NULL, 1)) > + return -EINVAL; Hmm, this check is too permissive, no? E.g. what happens if you move a link local address from one interface to another? In this case this code would still allow the saddr to be used. I just also quickly read up on the history (sorry was travelling last week) and wonder if you ever saw a user space facing bug or if this is basically some difference you saw while writing out of tree code? Thanks, Hannes
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