[PATCH 3.16 022/305] libertas_tf: prevent underflow in process_cmdrequest()

[Ben Hutchings]

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

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

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

commit 3348ef6a6a126706d6a73ed40c18d8033df72783 upstream.

If recvlength is less than MESSAGE_HEADER_LEN (4) we would end up
corrupting memory.

Fixes: c305a19a0d0a ("libertas_tf: usb specific functions")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/net/wireless/libertas_tf/if_usb.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/net/wireless/libertas_tf/if_usb.c
+++ b/drivers/net/wireless/libertas_tf/if_usb.c
@@ -610,9 +610,10 @@ static inline void process_cmdrequest(in
 				      struct if_usb_card *cardp,
 				      struct lbtf_private *priv)
 {
-	if (recvlength > LBS_CMD_BUFFER_SIZE) {
+	if (recvlength < MESSAGE_HEADER_LEN ||
+	    recvlength > LBS_CMD_BUFFER_SIZE) {
 		lbtf_deb_usbd(&cardp->udev->dev,
-			     "The receive buffer is too large\n");
+			     "The receive buffer is invalid: %d\n", recvlength);
 		kfree_skb(skb);
 		return;
 	}