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[146.241.225.251]) by smtp.gmail.com with ESMTPSA id op51-20020a05620a537300b00767dc4c539bsm4136811qkn.44.2023.08.01.06.34.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Aug 2023 06:34:10 -0700 (PDT) Message-ID: <8a7772a50a16fbbcb82fc0c5e09f9e31f3427e3d.camel@redhat.com> Subject: Re: [PATCH net-next v5 4/4] vsock/virtio: MSG_ZEROCOPY flag support From: Paolo Abeni To: Arseniy Krasnov , Stefan Hajnoczi , Stefano Garzarella , "David S. Miller" , Eric Dumazet , Jakub Kicinski , "Michael S. Tsirkin" , Jason Wang , Bobby Eshleman Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@sberdevices.ru, oxffffaa@gmail.com Date: Tue, 01 Aug 2023 15:34:07 +0200 In-Reply-To: <20230730085905.3420811-5-AVKrasnov@sberdevices.ru> References: <20230730085905.3420811-1-AVKrasnov@sberdevices.ru> <20230730085905.3420811-5-AVKrasnov@sberdevices.ru> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.46.4 (3.46.4-1.fc37) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 =3D skb_put(skb, len); > + err =3D 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... > + return 0; > + } > +} [...] > @@ -214,6 +251,70 @@ static u16 virtio_transport_get_type(struct sock *sk= ) > return VIRTIO_VSOCK_TYPE_SEQPACKET; > } > =20 > +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 =3D VIRTIO_VSOCK_SKB_HEADROOM; > + > + if (!zcopy) > + skb_len +=3D payload_len; > + > + skb =3D 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 =3D=3D NULL && (info->msg && payload_len > 0) && zcopy ??? If so it looks like skb can go through __zerocopy_sg_from_iter() even without a prior skb_set_owner_w()... Cheers, Paolo