From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Daniel Borkmann <daniel@iogearbox.net>,
Luigi Rizzo <lrizzo@google.com>,
netdev@vger.kernel.org
Cc: Jesper Dangaard Brouer <hawk@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
sameehj@amazon.com
Subject: Re: [PATCH] net-xdp: netdev attribute to control xdpgeneric skb linearization
Date: Thu, 23 Jan 2020 17:14:29 +0100 [thread overview]
Message-ID: <87blqui1zu.fsf@toke.dk> (raw)
In-Reply-To: <953c8fee-91f0-85e7-6c7b-b9a2f8df5aa6@iogearbox.net>
Daniel Borkmann <daniel@iogearbox.net> writes:
> On 1/23/20 10:53 AM, Toke Høiland-Jørgensen wrote:
>> Luigi Rizzo <lrizzo@google.com> writes:
>>
>>> Add a netdevice flag to control skb linearization in generic xdp mode.
>>> Among the various mechanism to control the flag, the sysfs
>>> interface seems sufficiently simple and self-contained.
>>> The attribute can be modified through
>>> /sys/class/net/<DEVICE>/xdp_linearize
>>> The default is 1 (on)
>
> Needs documentation in Documentation/ABI/testing/sysfs-class-net.
>
>> Erm, won't turning off linearization break the XDP program's ability to
>> do direct packet access?
>
> Yes, in the worst case you only have eth header pulled into linear
> section. :/
In which case an eBPF program could read/write out of bounds since the
verifier only verifies checks against xdp->data_end. Right?
> In tc/BPF for direct packet access we have bpf_skb_pull_data() helper
> which can pull in up to X bytes into linear section on demand. I guess
> something like this could be done for XDP context as well, e.g.
> generic XDP would pull when non-linear and native XDP would have
> nothing todo (though in this case you end up writing the prog
> specifically for generic XDP with slowdown when you'd load it on
> native XDP where it's linear anyway, but that could/should be
> documented if so).
Yeah, I really don't think this is a good idea; there are enough gotchas
with the difference between generic and native XDP as it is... :/
-Toke
next prev parent reply other threads:[~2020-01-23 16:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-22 20:32 [PATCH] net-xdp: netdev attribute to control xdpgeneric skb linearization Luigi Rizzo
2020-01-23 9:53 ` Toke Høiland-Jørgensen
2020-01-23 15:48 ` Daniel Borkmann
2020-01-23 16:14 ` Toke Høiland-Jørgensen [this message]
2020-01-23 17:30 ` Luigi Rizzo
2020-01-23 18:01 ` Toke Høiland-Jørgensen
2020-01-23 18:06 ` Luigi Rizzo
2020-01-23 21:36 ` Daniel Borkmann
2020-01-24 9:57 ` Toke Høiland-Jørgensen
2020-01-24 14:31 ` Luigi Rizzo
2020-01-24 15:30 ` Toke Høiland-Jørgensen
2020-01-24 17:15 ` Luigi Rizzo
2020-01-24 21:27 ` Toke Høiland-Jørgensen
2020-02-05 15:36 ` Luigi Rizzo
[not found] ` <CA+hQ2+hnqifXzyHjjc5TXJmJz_EVCbuF6vGchKjaWccfK2ZA4g@mail.gmail.com>
2020-02-05 15:55 ` Toke Høiland-Jørgensen
2020-01-23 17:25 ` Luigi Rizzo
2020-01-23 18:00 ` Toke Høiland-Jørgensen
2020-01-23 18:11 ` Luigi Rizzo
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