From: David Ahern <dsahern@gmail•com>
To: Stefano Brivio <sbrivio@redhat•com>
Cc: David Miller <davem@davemloft•net>,
Martin KaFai Lau <kafai@fb•com>, Jianlin Shi <jishi@redhat•com>,
Wei Wang <weiwan@google•com>, Eric Dumazet <edumazet@google•com>,
Matti Vaittinen <matti.vaittinen@fi•rohmeurope.com>,
netdev@vger•kernel.org
Subject: Re: [PATCH net v4 1/8] ipv4/fib_frontend: Rename ip_valid_fib_dump_req, provide non-strict version
Date: Mon, 17 Jun 2019 07:18:10 -0600 [thread overview]
Message-ID: <f6ed8beb-0892-059a-2b08-90e782226115@gmail.com> (raw)
In-Reply-To: <20190615052705.66f3fe62@redhat.com>
On 6/14/19 9:27 PM, Stefano Brivio wrote:
>>>> Can you explain why this patch is needed? The existing function requires
>>>> strict mode and is needed to enable any of the kernel side filtering
>>>> beyond the RTM_F_CLONED setting in rtm_flags.
>>>
>>> It's mostly to have proper NLM_F_MATCH support. Let's pick an iproute2
>>> version without strict checking support (< 5.0), that sets NLM_F_MATCH
>>> though. Then we need this check:
>>>
>>> if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*rtm)))
>>
>> but that check existed long before any of the strict checking and kernel
>> side filtering was added.
>
> Indeed. And now I'm recycling it, even if strict checking is not
> requested.
>
>>> and to set filter parameters not just based on flags (i.e. RTM_F_CLONED),
>>> but also on table, protocol, etc.
>>
>> and to do that you *must* have strict checking. There is no way to trust
>> userspace without that strict flag set because iproute2 for the longest
>> time sent the wrong header for almost all dump requests.
>
> So you're implying that:
>
> - we shouldn't support NLM_F_MATCH
>
> - we should keep this broken for iproute2 < 5.0.0?
>
> I guess this might be acceptable, but please state it clearly.
>
> By the way, if really needed, we can do strict checking even if not
> requested. But this might add more and more userspace breakage, I guess.
>
Prior to 5.0 and strict checking, iproute2 was sending ifinfomsg as the
header struct - which is wrong for routes. ifi_flags just happens to
have the same offset as rtm_flags so the check for RTM_F_CLONED is ok,
but nothing else sent in the get request (e.g., potentially appended
attributes) can be trusted, so the !strict path you are adding with
nlmsg_parse_deprecated is wrong. The kernel side filter argument can be
used and treating RTM_F_CLONED as a filter is ok, but not the new
parsing code.
next prev parent reply other threads:[~2019-06-17 13:18 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-15 1:32 [PATCH net v4 0/8] Fix listing (IPv4, IPv6) and flushing (IPv6) of cached route exceptions Stefano Brivio
2019-06-15 1:32 ` [PATCH net v4 1/8] ipv4/fib_frontend: Rename ip_valid_fib_dump_req, provide non-strict version Stefano Brivio
2019-06-15 2:54 ` David Ahern
2019-06-15 3:13 ` Stefano Brivio
2019-06-15 3:16 ` David Ahern
2019-06-15 3:27 ` Stefano Brivio
2019-06-16 20:04 ` Stefano Brivio
2019-06-17 13:38 ` David Ahern
2019-06-17 14:13 ` Stefano Brivio
2019-06-17 17:06 ` David Ahern
2019-06-17 18:28 ` Stefano Brivio
2019-06-17 13:18 ` David Ahern [this message]
2019-06-15 1:32 ` [PATCH net v4 2/8] ipv4: Honour NLM_F_MATCH, make semantics of NETLINK_GET_STRICT_CHK consistent Stefano Brivio
2019-06-15 3:13 ` David Ahern
2019-06-15 3:23 ` Stefano Brivio
2019-06-17 13:29 ` David Ahern
2019-06-15 1:32 ` [PATCH net v4 3/8] ipv4/fib_frontend: Allow RTM_F_CLONED flag to be used for filtering Stefano Brivio
2019-06-15 1:32 ` [PATCH 4/8] ipv4: Dump routed caches if requested Stefano Brivio
2019-06-15 1:32 ` [PATCH 5/8] Revert "net/ipv6: Bail early if user only wants cloned entries" Stefano Brivio
2019-06-15 1:32 ` [PATCH 6/8] ipv6: Honour NLM_F_MATCH, make semantics of NETLINK_GET_STRICT_CHK consistent Stefano Brivio
2019-06-15 1:32 ` [PATCH 7/8] ipv6: Dump route exceptions too in rt6_dump_route() Stefano Brivio
2019-06-15 1:32 ` [PATCH 8/8] ip6_fib: Don't discard nodes with valid routing information in fib6_locate_1() Stefano Brivio
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