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Message-ID: <1410172092.11872.85.camel@edumazet-glaptop2.roam.corp.google.com> Date: Mon, 08 Sep 2014 03:28:12 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: nicolas.dichtel@...nd.com Cc: David Miller <davem@...emloft.net>, therbert@...gle.com, alexander.h.duyck@...el.com, netdev@...r.kernel.org Subject: Re: [PATCH net] ipv6: refresh rt6i_genid in ip6_pol_route() On Mon, 2014-09-08 at 10:11 +0200, Nicolas Dichtel wrote: > Le 08/09/2014 07:07, Eric Dumazet a écrit : > > On Sun, 2014-09-07 at 21:59 -0700, David Miller wrote: > >> From: Eric Dumazet <eric.dumazet@...il.com> > >> Date: Sun, 07 Sep 2014 21:43:54 -0700 > >> > >>> On Sun, 2014-09-07 at 21:27 -0700, David Miller wrote: > >>>> From: Eric Dumazet <eric.dumazet@...il.com> > >>>> Date: Sun, 07 Sep 2014 21:18:25 -0700 > >>>> > >>>>> On Sun, 2014-09-07 at 15:54 -0700, David Miller wrote: > >>>>> > >>>>>> This might be broken. > >>>>>> > >>>>>> We are dealing here with persistent entries in the ipv6 routine trie. > >>>>>> > >>>>>> If you just bump the genid on the next person to look it up, other > >>>>>> sockets and cached entities might not have validated the route yet, > >>>>>> and now will falsely see the route as valid. We have to ensure that > >>>>>> they too drop this route and perform a relookup. > >>>>> > >>>>> I am confused, I thought it was the role of the cookie. > >>>>> > >>>>> (Ie socket has to store its own cookie to be able to validate a route) > >>>>> > >>>>> Before 6f3118b571b8 patch, how was this done anyway ? > >>>>> > >>>>> If persistent routes cannot refresh the genid, then they are useless ? > >>>> > >>>> I just speak about the genid aspect. > >>>> > >>>> I understand that cookie (via node->fn_sernum) invalidates the path > >>>> in the fib_trie, but the genid protects against other circumstances > >>>> (matching IPSEC rule, f.e.) > >>>> > >>>> You have to make sure all other sockets did a full route lookup > >>>> (including IPSEC) before you can safely adjust the genid. > >>>> > >>>> I could be wrong, recheck my analysis please :-) > >>> > >>> So this whole genid protection can not work, unless we make sure a > >>> socket cannot share a route with another socket. > >>> > >>> This means we have to clone all routes. > >> > >> I'm willing to revert the change in question if you think that's the > >> sanest way forward. > >> > >> The bug fix for more obscure use cases (IPSEC) if pointless if it > >> breaks more common things (TCP input route caching). > > > > Lets wait for Nicolas and/or Hannes input, they might have some ideas... > > The initial problem was in SCTP. Here is the thread after the v1 patch: > http://patchwork.ozlabs.org/patch/182235/ > > Before the patch, SCTP stored the IPv6 route in its cache and if an IPsec > rules was inserted after that operation, SCTP never invalidated the cached > route to use a new xfrm route. This thread mentions output route. The problem I currently have with IPv6 early demux is for input routes. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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