From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 BB423410D2C for ; Thu, 30 Apr 2026 13:04:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777554287; cv=none; b=Q+stWn6cHveGX6pw5b+DQTd3T3u2q42NnZFNtFzbZo6a5LqduQ3evRgE20UlL+4icfoTrc3VtWl1L00vITDd6TbwhNpRnIoFYd6V9ejQk9cIZbMfGNekerfDKJCCEfO88VI9siW4kgrLHA7BXvGz/EKINdyMutJU682TkRNyEgw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777554287; c=relaxed/simple; bh=Dk9brHbKfFNbGJGzioI4SNCia5lWoLEHi0LrGbaPeqU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kmXfiGMFdqxLuAm6yBtGrdPihzJ5xBBAOv0e9CammeZpswn1Ok/5F5M1mumGddNvcN6D/g0uXIgOUpGmWqIPfRKZ2U9jbDceZrz0SyamQeIicKaZtpHI5Yh+5UhIaD1ZnHLS3mP+nFgjbFJ+v0pTY907+mf0ap5RSmSOfHEF+A8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=RXk73A5o; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b=POTcm97i; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RXk73A5o"; dkim=pass (2048-bit key) header.d=redhat.com header.i=@redhat.com header.b="POTcm97i" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1777554285; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=4iM1C5bPOK6CsY7bMqOIntIdxAE/svN63ooTIzddU6M=; b=RXk73A5ow/64w2OgioGVZ7UcocN10toDVv4zpYwlnfa3D/vUk8QHLSqZFNtTles62H/gO7 3u6G6E4H4mc18RLAMmfTwRZ9yb0aReYu7FeTir8N3FRehmu2Z0691rtVRT+gXUOpwXXHbd fvlnSBMqb2IIkpWlH1pZBveLfFutj04= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-648-ofp_N2UdPlCfIk8UtiUHFg-1; Thu, 30 Apr 2026 09:04:43 -0400 X-MC-Unique: ofp_N2UdPlCfIk8UtiUHFg-1 X-Mimecast-MFC-AGG-ID: ofp_N2UdPlCfIk8UtiUHFg_1777554282 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-488d9e1e61aso9721825e9.0 for ; Thu, 30 Apr 2026 06:04:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=google; t=1777554282; x=1778159082; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=4iM1C5bPOK6CsY7bMqOIntIdxAE/svN63ooTIzddU6M=; b=POTcm97iezuPZHqF0RvZ1r7OFeiV8TDsuFww9kPOTy5qXjT6k+smCN2BzrSSRP2zRX YMYHmpLE4gqRM4OrBSpe2pGideFti0061hbCb5Sw/T9AJ5cW49YqtaprYa5fBbnNrDPD ayjK//nCMh6OjbCNexe1Hllnk7K7DQ3XdXAkSU8+HKvyrJ2SQ/Tox1ZQvb8iLnDsJDNY V5Taor7rsLr1ehAiKoKRP/7bRt4zN3TTzTHDQmnHsqT+ffKvdx5vpcika7oxNs7SLbpS Ku6+BUag+ciarVWBDfaCPCe1N9Q1AEpV4fCfhCDbR2cJWyM9ftP6xY+j0bkdSatTVUQD SGPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777554282; x=1778159082; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=4iM1C5bPOK6CsY7bMqOIntIdxAE/svN63ooTIzddU6M=; b=WHk7DOxQRDLmldkOQNd6fxayNxiJCzfHb7+Kd2N5uablHe4MO5GDmDyoolsIEFUOn9 FNc/+muiN+dsN/0ETkbHjWGkj9YRkYr2F0l/vNU9DodD/NITNPhlirYDLelsyQ3j2+yT EQPd0m/58HQL1/PROeaSFveNFTmX7YNoCNDy7TQKK14FqxtGEpblzHIShhyQqUatseRQ CgMjSBnXUkvtslOXsLUh2Y4VmD6R/lRYgeZ1iN/sGiEAXxXKpttguf+8w6zbUpRj7ve5 BOpZqDFrzaobeVHGZJ6gvHcdaidcDmqnZ4oJdNcDhpfr626Cs2OcO/BFO6cqQ1vcV1/F OwxQ== X-Forwarded-Encrypted: i=1; AFNElJ/pll3L0L8ERrg72kwhkgUFqf4BpaOj5eYmRxGfeXgZ/4OCMwy+YmMDOGH6EgTCXjrhjk1xuNuAEeHyvGI=@vger.kernel.org X-Gm-Message-State: AOJu0YzC/NNqFro/6Kqtedsa4Emw/7NMih8QdAyDWdwGKFlx63ftpoMw 4fQy4JDrquq2OgEY8GjGc6ncrfJG26AxlsaNqk3t3jXS9J9TJaCw3j6GkCXIGK4ELSY/A+Yek0s vZ7oR1DGXmzf+t26c4DYLTaUcIiaXvCLh/F/d71ToTS9C5AGSHJ1qFEljAiL8O6o0wQ== X-Gm-Gg: AeBDiesrzRTMD+5xgsbrsQHbTfMsvdJ6XyHzT/QDroTFh5o6L5xOQnvrg4XNlpuKJm2 ZFOr4uf0+z5+GakI7LSjLUNtfRIHYi6vaVONKE0BCaCtYeMthqxiITSGVKxfc3i1oYLbAGNzIUN 0lCklKXjnRwn6MkUo8AMJAg7/NlJoRPnuLwRJa6yxs2oC5MgTiyitV+SIukoavWFfkMpH/FjRhl ff3fJZ7LWU8vimd+JbQ50pJI6NGKAGks8PWFB+AwxZZQ6oewhfWdIBVF4rXoA6A0B+6n9tQIYw5 PJnN4C8LK2MUmIiFAy9WVlQbc4rFVCfjE9VIyfxPSVtE5BOZSn+/Hy1xN/9iJ0B4R5aec5merpO Y3zJRa0z03sEH9bielySvA/rJrKHr0aFCWcqBsQ== X-Received: by 2002:a05:600c:6992:b0:48a:56de:d62a with SMTP id 5b1f17b1804b1-48a83d7b059mr51482215e9.11.1777554281980; Thu, 30 Apr 2026 06:04:41 -0700 (PDT) X-Received: by 2002:a05:600c:6992:b0:48a:56de:d62a with SMTP id 5b1f17b1804b1-48a83d7b059mr51481435e9.11.1777554281407; Thu, 30 Apr 2026 06:04:41 -0700 (PDT) Received: from leonardi-redhat ([176.206.19.176]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a82301b7bsm71336415e9.11.2026.04.30.06.04.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2026 06:04:40 -0700 (PDT) Date: Thu, 30 Apr 2026 15:04:37 +0200 From: Luigi Leonardi To: Yiqi Sun Cc: kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stefanha@redhat.com, sgarzare@redhat.com, mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Subject: Re: [PATCH] vsock/virtio: fix vsockmon info leak in non-linear tap copy Message-ID: References: <20260430071110.380509-1-sunyiqixm@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20260430071110.380509-1-sunyiqixm@gmail.com> On Thu, Apr 30, 2026 at 03:11:10PM +0800, Yiqi Sun wrote: >vsockmon mirrors packets through virtio_transport_build_skb(), which >builds a new skb and copies the payload into it. For non-linear skbs, >this goes through virtio_transport_copy_nonlinear_skb(). > >Helper manually initializes a iov_iter, but leaves iov_iter.count unset. >As a result, skb_copy_datagram_iter() sees zero writable bytes >in the destination iterator and copies no payload data. > >This becomes an info leak because virtio_transport_build_skb() has >already reserved payload_len bytes in the new skb with skb_put(). The >skb is then returned to the tap path with that payload area still >uninitialized, so userspace reading from a vsockmon device can observe >heap contents and potentially kernel address. > >Fix it by initializing iov_iter.count to the number of bytes to copy. > >Fixes: 4b0bf10eb077 ("vsock/virtio: non-linear skb handling for tap") >Signed-off-by: Yiqi Sun >--- > net/vmw_vsock/virtio_transport_common.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c >index 416d533f493d..6b26ee57ccab 100644 >--- a/net/vmw_vsock/virtio_transport_common.c >+++ b/net/vmw_vsock/virtio_transport_common.c >@@ -152,7 +152,7 @@ static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb, > iov_iter.nr_segs = 1; > > to_copy = min_t(size_t, len, skb->len); >- >+ iov_iter.count = to_copy; > skb_copy_datagram_iter(skb, VIRTIO_VSOCK_SKB_CB(skb)->offset, > &iov_iter, to_copy); > } >-- >2.34.1 > Thanks for the fix! Tested using vsock_loopback sending zero-copy packets. Payload is always zero before the fix. Reviewed-by: Luigi Leonardi