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From:   Alvaro Karsz <alvaro.karsz@solid-run.com>
To:     Xuan Zhuo <xuanzhuo@linux.alibaba.com>
CC:     "davem@davemloft.net" <davem@davemloft.net>,
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Subject: Re: [PATCH net] virtio-net: reject small vring sizes
Thread-Topic: [PATCH net] virtio-net: reject small vring sizes
Thread-Index: AQHZcDeGnH5xR2OGlkuo4s6jvhNMC68uvmIAgABRFeY=
Date:   Mon, 17 Apr 2023 06:47:58 +0000
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References: <20230416074607.292616-1-alvaro.karsz@solid-run.com>
 <1681696410.7972026-1-xuanzhuo@linux.alibaba.com>
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> > Check vring size and fail probe if a transmit/receive vring size is=0A=
> > smaller than MAX_SKB_FRAGS + 2.=0A=
> >=0A=
> > At the moment, any vring size is accepted. This is problematic because=
=0A=
> > it may result in attempting to transmit a packet with more fragments=0A=
> > than there are descriptors in the ring.=0A=
> =0A=
> So, why we check the rx ring?=0A=
> =0A=
=0A=
You're right, the rx check should be a little more complicated.=0A=
It depends on the negotiated features, like VIRTIO_NET_F_MTU, any guest GSO=
, VIRTIO_NET_F_MRG_RXBUF.=0A=
But MAX_SKB_FRAGS + 2 covers all the rx scenarios.=0A=
We may be able to accept smaller rx rings if for example none of the above =
features are negotiated.=0A=
=0A=
If you think that this is necessary, we can do a more complex rx check.=