[PATCH net-next, 2/2] hv_netvsc: Add range checking for rx packet offset and length

[Haiyang Zhang <haiyangz@linuxonhyperv.com>]

From: Haiyang Zhang <haiyangz@microsoft.com>

This patch adds range checking for rx packet offset and length.
It may only happen if there is a host side bug.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 drivers/net/hyperv/hyperv_net.h |  1 +
 drivers/net/hyperv/netvsc.c     | 17 +++++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 0db3bd1ea06f..49c05ac894e5 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -793,6 +793,7 @@ struct netvsc_device {
 
 	/* Receive buffer allocated by us but manages by NetVSP */
 	void *recv_buf;
+	u32 recv_buf_size; /* allocated bytes */
 	u32 recv_buf_gpadl_handle;
 	u32 recv_section_cnt;
 	u32 recv_section_size;
diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
index 1ddb2c39b6e4..a6700d65f206 100644
--- a/drivers/net/hyperv/netvsc.c
+++ b/drivers/net/hyperv/netvsc.c
@@ -289,6 +289,8 @@ static int netvsc_init_buf(struct hv_device *device,
 		goto cleanup;
 	}
 
+	net_device->recv_buf_size = buf_size;
+
 	/*
 	 * Establish the gpadl handle for this buffer on this
 	 * channel.  Note: This call uses the vmbus connection rather
@@ -1095,11 +1097,22 @@ static int netvsc_receive(struct net_device *ndev,
 
 	/* Each range represents 1 RNDIS pkt that contains 1 ethernet frame */
 	for (i = 0; i < count; i++) {
-		void *data = recv_buf
-			+ vmxferpage_packet->ranges[i].byte_offset;
+		u32 offset = vmxferpage_packet->ranges[i].byte_offset;
 		u32 buflen = vmxferpage_packet->ranges[i].byte_count;
+		void *data;
 		int ret;
 
+		if (unlikely(offset + buflen > net_device->recv_buf_size)) {
+			status = NVSP_STAT_FAIL;
+			netif_err(net_device_ctx, rx_err, ndev,
+				  "Packet offset:%u + len:%u too big\n",
+				  offset, buflen);
+
+			continue;
+		}
+
+		data = recv_buf + offset;
+
 		trace_rndis_recv(ndev, q_idx, data);
 
 		/* Pass it to the upper layer */
-- 
2.15.1

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