From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.rulkc.org (mail.rulkc.org [155.212.184.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D37CA3D88EC; Fri, 15 May 2026 17:18:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=155.212.184.193 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778865526; cv=none; b=Kc8w4U8lvvvEXh1wYTW96/eDgCmViUeHX7rZEeCnm0afxVFOByE5PDOuLJYPpuG1mMSL3CrcGhu9LsSc3i23I8DLKn6VrGP1375dePSAhw3oy7rVnlpAhYpx5+JUWKnYuforRc7BsFa4c+bt9KZriTnUApaERsze9LZZLpL2GA0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778865526; c=relaxed/simple; bh=AThb4VcvVIl2q1HLSzrRx+pOQEogMqaBF6o78sY7O9k=; h=Message-ID:Date:MIME-Version:In-Reply-To:To:Cc:From:Subject: Content-Type; b=gdcErAGZDc+f4cenwtMCTl+Hedle1W+fCSHJZrMGgo74xIJfQ3VwaYzxIHxH4xnkv5rKe9QOJnmsyQUnO9uqDoKwTurs+tQQ8s9GARFMRzKmwYaGIUMX2ll5LDEtyFjyO39HYu8ipwfPwRF4PAMiNdytMHumcts7AuYEzBUyuzg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=rulkc.org; spf=pass smtp.mailfrom=rulkc.org; dkim=pass (2048-bit key) header.d=rulkc.org header.i=@rulkc.org header.b=bMjmi7p3; arc=none smtp.client-ip=155.212.184.193 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=rulkc.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rulkc.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rulkc.org header.i=@rulkc.org header.b="bMjmi7p3" Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 18E0310113F; Fri, 15 May 2026 20:18:26 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rulkc.org; s=dkim; t=1778865514; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to; bh=y4uy4Pn148gEWMp6CsBHAvnIqyb+WyfkRqF4BSbh4/E=; b=bMjmi7p3G3dFTYfn9vrSaMz3B4xgHlRxlpV/RN1261UCXil+PYgyODOy8Fsdo0qFG2p9hQ ykboWeIQBNEhnUTG1AIrWpk1KPoB8bbx2KnpXNKUQI3wohBPlA9m34jr9d63oe3kEapVaZ jSyV2bNO9YKyQhkDgjJKvyAsN++/CAjnkjEPU54gIwUi+qPhDF5J/EqOmLG8od0x4MpvSp mQLOoCCekeefOpefQCWsqXBuMnAYrqezaDw0sycVuFNct/RA/vxir36l35FeAQZIwe70VL WlJoS0AxqtjZ6kzufsdF+KOqaJ2cCcj1NY+e9crweb8KF62BsTeB10kSc06gZQ== Message-ID: <1546ca10-e85b-4a67-a5b9-cf2623d11e7c@rulkc.org> Date: Fri, 15 May 2026 20:18:18 +0300 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: ru In-Reply-To: <20260514092948.268720-1-sgarzare@redhat.com> To: Stefano Garzarella Cc: netdev@vger.kernel.org, Jakub Kicinski , "Paolo Abeni," , Simon Horman , Stefan Hajnoczi , kvm@vger.kernel.org, Eric Dumazet , "Xuan Zhuo," , virtualization@lists.linux.dev, "David S., Miller" , Jason Wang , linux-kernel@vger.kernel.org, Maher Azzouzi , eperezma@redhat.com From: Arseniy Krasnov Subject: Re: [PATCH net] vsock/virtio: fix zerocopy completion for multi-skb sends Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Last-TLS-Session-Version: TLSv1.3 > From: Stefano Garzarella > > When a large message is fragmented into multiple skbs, the zerocopy > uarg is only allocated and attached to the last skb in the loop. > Non-final skbs carry pinned user pages with no completion tracking, > so the kernel has no way to notify userspace when those pages are safe > to reuse. If the loop breaks early the uarg is never allocated at all, > leaking pinned pages with no completion notification. > > Fix this by following the approach used by TCP: allocate the zerocopy > uarg (if not provided by the caller) before the send loop and attach > it to every skb via skb_zcopy_set(), which takes a reference per skb. > Each skb's completion properly decrements the refcount, and the > notification only fires after the last skb is freed. > On failure, if no data was sent, the uarg is cleanly aborted via > net_zcopy_put_abort(). > > This issue was initially discovered by sashiko while reviewing commit > 1cb36e252211 ("vsock/virtio: fix MSG_ZEROCOPY pinned-pages accounting") > but was pre-existing. > > Fixes: 581512a6dc93 ("vsock/virtio: MSG_ZEROCOPY flag support") > Cc: Arseniy Krasnov > Closes: https://sashiko.dev/#/patchset/20260420132051.217589-1-sgarzare%40redhat.com > Reported-by: Maher Azzouzi > Signed-off-by: Stefano Garzarella Acked-by: Arseniy Krasnov > --- > net/vmw_vsock/virtio_transport_common.c | 83 ++++++++++--------------- > 1 file changed, 34 insertions(+), 49 deletions(-) > > diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c > index 989cc252d3d3..1e3409d28164 100644 > --- a/net/vmw_vsock/virtio_transport_common.c > +++ b/net/vmw_vsock/virtio_transport_common.c > @@ -70,34 +70,6 @@ static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops, > return true; > } > > -static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk, > - struct sk_buff *skb, > - struct msghdr *msg, > - size_t pkt_len, > - bool zerocopy) > -{ > - struct ubuf_info *uarg; > - > - if (msg->msg_ubuf) { > - uarg = msg->msg_ubuf; > - net_zcopy_get(uarg); > - } else { > - struct ubuf_info_msgzc *uarg_zc; > - > - uarg = msg_zerocopy_realloc(sk_vsock(vsk), > - pkt_len, NULL, false); > - if (!uarg) > - return -1; > - > - uarg_zc = uarg_to_msgzc(uarg); > - uarg_zc->zerocopy = zerocopy ? 1 : 0; > - } > - > - skb_zcopy_init(skb, uarg); > - > - return 0; > -} > - > static int virtio_transport_fill_skb(struct sk_buff *skb, > struct virtio_vsock_pkt_info *info, > size_t len, > @@ -317,8 +289,10 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > u32 src_cid, src_port, dst_cid, dst_port; > const struct virtio_transport *t_ops; > struct virtio_vsock_sock *vvs; > + struct ubuf_info *uarg = NULL; > u32 pkt_len = info->pkt_len; > bool can_zcopy = false; > + bool have_uref = false; > u32 rest_len; > int ret; > > @@ -360,6 +334,25 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > if (can_zcopy) > max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, > (MAX_SKB_FRAGS * PAGE_SIZE)); > + > + if (info->msg->msg_flags & MSG_ZEROCOPY && > + info->op == VIRTIO_VSOCK_OP_RW) { > + uarg = info->msg->msg_ubuf; > + > + if (!uarg) { > + uarg = msg_zerocopy_realloc(sk_vsock(vsk), > + pkt_len, NULL, false); > + if (!uarg) { > + virtio_transport_put_credit(vvs, pkt_len); > + return -ENOMEM; > + } > + > + if (!can_zcopy) > + uarg_to_msgzc(uarg)->zerocopy = 0; > + > + have_uref = true; > + } > + } > } > > rest_len = pkt_len; > @@ -378,27 +371,7 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > break; > } > > - /* We process buffer part by part, allocating skb on > - * each iteration. If this is last skb for this buffer > - * and MSG_ZEROCOPY mode is in use - we must allocate > - * completion for the current syscall. > - * > - * Pass pkt_len because msg iter is already consumed > - * by virtio_transport_fill_skb(), so iter->count > - * can not be used for RLIMIT_MEMLOCK pinned-pages > - * accounting done by msg_zerocopy_realloc(). > - */ > - if (info->msg && info->msg->msg_flags & MSG_ZEROCOPY && > - skb_len == rest_len && info->op == VIRTIO_VSOCK_OP_RW) { > - if (virtio_transport_init_zcopy_skb(vsk, skb, > - info->msg, > - pkt_len, > - can_zcopy)) { > - kfree_skb(skb); > - ret = -ENOMEM; > - break; > - } > - } > + skb_zcopy_set(skb, uarg, NULL); > > virtio_transport_inc_tx_pkt(vvs, skb); > > @@ -422,6 +395,18 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, > > virtio_transport_put_credit(vvs, rest_len); > > + /* msg_zerocopy_realloc() initializes the ubuf_info refcnt to 1. > + * skb_zcopy_set() increases it for each skb, so we can drop that > + * initial reference to keep it balanced. > + */ > + if (have_uref) { > + if (rest_len == pkt_len) > + /* No data sent, abort the notification. */ > + net_zcopy_put_abort(uarg, true); > + else > + net_zcopy_put(uarg); > + } > + > /* Return number of bytes, if any data has been sent. */ > if (rest_len != pkt_len) > ret = pkt_len - rest_len; > -- > 2.54.0 > >