On Tue, 2023-08-01 at 16:36 +0300, Arseniy Krasnov wrote:
>
> On 01.08.2023 16:34, Paolo Abeni wrote:
> > On Sun, 2023-07-30 at 11:59 +0300, Arseniy Krasnov wrote:
> > > +static int virtio_transport_fill_skb(struct sk_buff *skb,
> > > + struct virtio_vsock_pkt_info *info,
> > > + size_t len,
> > > + bool zcopy)
> > > +{
> > > + if (zcopy) {
> > > + return __zerocopy_sg_from_iter(info->msg, NULL, skb,
> > > + &info->msg->msg_iter,
> > > + len);
> > > + } else {
> >
> >
> > No need for an else statement after 'return'
> >
> > > + void *payload;
> > > + int err;
> > > +
> > > + payload = skb_put(skb, len);
> > > + err = memcpy_from_msg(payload, info->msg, len);
> > > + if (err)
> > > + return -1;
> > > +
> > > + if (msg_data_left(info->msg))
> > > + return 0;
> > > +
> >
> > This path does not update truesize, evem if it increases the skb len...
>
> Thanks, I'll fix it.
>
> >
> > > + return 0;
> > > + }
> > > +}
> >
> > [...]
> >
> > > @@ -214,6 +251,70 @@ static u16 virtio_transport_get_type(struct sock *sk)
> > > return VIRTIO_VSOCK_TYPE_SEQPACKET;
> > > }
> > >
> > > +static struct sk_buff *virtio_transport_alloc_skb(struct vsock_sock *vsk,
> > > + struct virtio_vsock_pkt_info *info,
> > > + size_t payload_len,
> > > + bool zcopy,
> > > + u32 src_cid,
> > > + u32 src_port,
> > > + u32 dst_cid,
> > > + u32 dst_port)
> > > +{
> > > + struct sk_buff *skb;
> > > + size_t skb_len;
> > > +
> > > + skb_len = VIRTIO_VSOCK_SKB_HEADROOM;
> > > +
> > > + if (!zcopy)
> > > + skb_len += payload_len;
> > > +
> > > + skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
> > > + if (!skb)
> > > + return NULL;
> > > +
> > > + virtio_transport_init_hdr(skb, info, src_cid, src_port,
> > > + dst_cid, dst_port,
> > > + payload_len);
> > > +
> > > + /* Set owner here, because '__zerocopy_sg_from_iter()' uses
> > > + * owner of skb without check to update 'sk_wmem_alloc'.
> > > + */
> > > + if (vsk)
> > > + skb_set_owner_w(skb, sk_vsock(vsk));
> >
> > ... which can lead to bad things(TM) if the skb goes trough some later
> > non trivial processing, due to the above skb_set_owner_w().
> >
> > Additionally can be the following condition be true:
> >
> > vsk == NULL && (info->msg && payload_len > 0) && zcopy
> >
> > ???
>
> No, vsk == NULL only when we reset connection, in that case both info->msg == NULL and payload_len == 0,
> as this is control message without any data.
Perhaps a comment with possibly even a WARN_ON_ONCE(!<the above>) could
help ;)
Thanks!
Paolo
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