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From:   "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>
To:     KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Michael Kelley <mikelley@microsoft.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     linux-hyperv@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>
Subject: [PATCH 1/5] hv_sock: Check hv_pkt_iter_first_raw()'s return value
Date:   Wed, 20 Apr 2022 22:07:16 +0200
Message-Id: <20220420200720.434717-2-parri.andrea@gmail.com>
In-Reply-To: <20220420200720.434717-1-parri.andrea@gmail.com>
References: <20220420200720.434717-1-parri.andrea@gmail.com>
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The function returns NULL if the ring buffer doesn't contain enough
readable bytes to constitute a packet descriptor.  The ring buffer's
write_index is in memory which is shared with the Hyper-V host, an
erroneous or malicious host could thus change its value and overturn
the result of hvs_stream_has_data().

Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
---
 net/vmw_vsock/hyperv_transport.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index e111e13b66604..943352530936e 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -603,6 +603,8 @@ static ssize_t hvs_stream_dequeue(struct vsock_sock *vsk, struct msghdr *msg,
 
 	if (need_refill) {
 		hvs->recv_desc = hv_pkt_iter_first_raw(hvs->chan);
+		if (!hvs->recv_desc)
+			return -ENOBUFS;
 		ret = hvs_update_recv_data(hvs);
 		if (ret)
 			return ret;
-- 
2.25.1