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

Ben Hutchings
2017-03-10T13:39:16Z

From: Anssi Hannula <anssi.hannula@bitwise.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@bitwise.fi>
Fixes: bb81b2ddfa19 ("net: add Xilinx emac lite device driver")
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.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++;