linux-kernel - [PATCH 3.16 300/370] net: xilinx_emaclite: fix receive buffer overflow

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Message-ID: <lsq.1489146383.871670918@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:23 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Anssi Hannula" <anssi.hannula@...wise.fi>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.16 300/370] net: xilinx_emaclite: fix receive buffer
 overflow

3.16.42-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Anssi Hannula <anssi.hannula@...wise.fi>

commit cd224553641848dd17800fe559e4ff5d208553e8 upstream.

xilinx_emaclite looks at the received data to try to determine the
Ethernet packet length but does not properly clamp it if
proto_type == ETH_P_IP or 1500 < proto_type <= 1518, causing a buffer
overflow and a panic via skb_panic() as the length exceeds the allocated
skb size.

Fix those cases.

Also add an additional unconditional check with WARN_ON() at the end.

Signed-off-by: Anssi Hannula <anssi.hannula@...wise.fi>
Fixes: bb81b2ddfa19 ("net: add Xilinx emac lite device driver")
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/ethernet/xilinx/xilinx_emaclite.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c
+++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
@@ -371,7 +371,7 @@ static int xemaclite_send_data(struct ne
  *
  * Return:	Total number of bytes received
  */
-static u16 xemaclite_recv_data(struct net_local *drvdata, u8 *data)
+static u16 xemaclite_recv_data(struct net_local *drvdata, u8 *data, int maxlen)
 {
 	void __iomem *addr;
 	u16 length, proto_type;
@@ -411,7 +411,7 @@ static u16 xemaclite_recv_data(struct ne
 
 	/* Check if received ethernet frame is a raw ethernet frame
 	 * or an IP packet or an ARP packet */
-	if (proto_type > (ETH_FRAME_LEN + ETH_FCS_LEN)) {
+	if (proto_type > ETH_DATA_LEN) {
 
 		if (proto_type == ETH_P_IP) {
 			length = ((ntohl(__raw_readl(addr +
@@ -419,6 +419,7 @@ static u16 xemaclite_recv_data(struct ne
 					XEL_RXBUFF_OFFSET)) >>
 					XEL_HEADER_SHIFT) &
 					XEL_RPLR_LENGTH_MASK);
+			length = min_t(u16, length, ETH_DATA_LEN);
 			length += ETH_HLEN + ETH_FCS_LEN;
 
 		} else if (proto_type == ETH_P_ARP)
@@ -431,6 +432,9 @@ static u16 xemaclite_recv_data(struct ne
 		/* Use the length in the frame, plus the header and trailer */
 		length = proto_type + ETH_HLEN + ETH_FCS_LEN;
 
+	if (WARN_ON(length > maxlen))
+		length = maxlen;
+
 	/* Read from the EmacLite device */
 	xemaclite_aligned_read((u32 __force *) (addr + XEL_RXBUFF_OFFSET),
 				data, length);
@@ -605,7 +609,7 @@ static void xemaclite_rx_handler(struct
 
 	skb_reserve(skb, 2);
 
-	len = xemaclite_recv_data(lp, (u8 *) skb->data);
+	len = xemaclite_recv_data(lp, (u8 *) skb->data, len);
 
 	if (!len) {
 		dev->stats.rx_errors++;