netdev - Re: [PATCH net 1/2] ipv6: Dump route exceptions too in rt6_dump

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 6 Jun 2019 17:19:49 -0600
From:   David Ahern <dsahern@...il.com>
To:     Stefano Brivio <sbrivio@...hat.com>, Martin Lau <kafai@...com>
Cc:     David Miller <davem@...emloft.net>, Jianlin Shi <jishi@...hat.com>,
        Wei Wang <weiwan@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net 1/2] ipv6: Dump route exceptions too in
 rt6_dump_route()

On 6/6/19 4:58 PM, Stefano Brivio wrote:
>>> This also means that to avoid sending duplicates in the case where at
>>> least one rt6_fill_node() call goes through and one fails, we would
>>> need to track the last bucket and entry sent, or, alternatively, to
>>> make sure we can fit the whole node before dumping.  
>> My another concern is the dump may never finish.
> 
> That's not a guarantee in general, even without this, because in theory
> the skb passed might be small enough that we can't even fit a single
> node without exceptions.

That should be handled by skb->len = 0 and then returning the err back
to caller. See inet_dump_fib.

> 
> We could add a guard on w->leaf not being the same before and after the
> walk in inet6_dump_fib() and, if it is, terminate the dump. I just
> wonder if we have to do this at all -- I can't find this being done
> anywhere else (at a quick look at least).
> 
> By the way, we can also trigger a never-ending dump by touching the
> tree frequently enough during a dump: it would always start again from
> the root, see fib6_dump_table().
> 

that should be a userspace problem on a sequence mismatch. In-kernel
notifiers do restart for offload drivers (seeregister_fib_notifier), but
as I recall the kernel should not restart a dump.

libnl reference is nl_cache_refill,

                err = nl_cache_pickup(sk, cache);
                if (err == -NLE_DUMP_INTR) {
                        NL_DBG(2, "Dump interrupted, restarting!\n");
                        goto restart;
                } else if (err < 0)
                        break;