net: usb: smsc75xx: Move packet length check to prevent kernel panic in skb_pull

Packet length check needs to be located after size and align_count
calculation to prevent kernel panic in skb_pull() in case
rx_cmd_a & RX_CMD_A_RED evaluates to true.

Fixes: d8b228318935 ("net: usb: smsc75xx: Limit packet length to skb->len")
Signed-off-by: Szymon Heidrich <szymon.heidrich@gmail.com>
Link: https://lore.kernel.org/r/20230316110540.77531-1-szymon.heidrich@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/usb/smsc75xx.c b/drivers/net/usb/smsc75xx.c
index db34f8d..5d6454f 100644 (file)
--- a/drivers/net/usb/smsc75xx.c
+++ b/drivers/net/usb/smsc75xx.c
@@ -2200,6 +2200,13 @@ static int smsc75xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
                size = (rx_cmd_a & RX_CMD_A_LEN) - RXW_PADDING;
                align_count = (4 - ((size + RXW_PADDING) % 4)) % 4;
 
+               if (unlikely(size > skb->len)) {
+                       netif_dbg(dev, rx_err, dev->net,
+                                 "size err rx_cmd_a=0x%08x\n",
+                                 rx_cmd_a);
+                       return 0;
+               }
+
                if (unlikely(rx_cmd_a & RX_CMD_A_RED)) {
                        netif_dbg(dev, rx_err, dev->net,
                                  "Error rx_cmd_a=0x%08x\n", rx_cmd_a);
@@ -2212,8 +2219,7 @@ static int smsc75xx_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
                                dev->net->stats.rx_frame_errors++;
                } else {
                        /* MAX_SINGLE_PACKET_SIZE + 4(CRC) + 2(COE) + 4(Vlan) */
-                       if (unlikely(size > (MAX_SINGLE_PACKET_SIZE + ETH_HLEN + 12) ||
-                                    size > skb->len)) {
+                       if (unlikely(size > (MAX_SINGLE_PACKET_SIZE + ETH_HLEN + 12))) {
                                netif_dbg(dev, rx_err, dev->net,
                                          "size err rx_cmd_a=0x%08x\n",
                                          rx_cmd_a);