From 9becd707841207652449a8dfd90fe9c476d88546 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Bj=C3=B8rn=20Mork?= Date: Fri, 2 May 2014 23:27:00 +0200 Subject: [PATCH] net: cdc_ncm: fix buffer overflow MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Commit 4d619f625a60 ("net: cdc_ncm: no point in filling up the NTBs if we send ZLPs") changed the padding logic for devices with the ZLP flag set. This meant that frames of any size will be sent without additional padding, except for the single byte added if the size is a multiple of the USB packet size. But if the unpadded size is identical to the maximum frame size, and the maximum size is a multiplum of the USB packet size, then this one-byte padding will overflow the buffer. Prevent padding if already at maximum frame size, letting usbnet transmit a ZLP instead in this case. Fixes: 4d619f625a60 ("net: cdc_ncm: no point in filling up the NTBs if we send ZLPs") Reported by: Yu-an Shih Signed-off-by: Bjørn Mork Signed-off-by: David S. Miller --- drivers/net/usb/cdc_ncm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index 549dbac710ed..9a2bd11943eb 100644 --- a/drivers/net/usb/cdc_ncm.c +++ b/drivers/net/usb/cdc_ncm.c @@ -785,7 +785,7 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign) skb_out->len > CDC_NCM_MIN_TX_PKT) memset(skb_put(skb_out, ctx->tx_max - skb_out->len), 0, ctx->tx_max - skb_out->len); - else if ((skb_out->len % dev->maxpacket) == 0) + else if (skb_out->len < ctx->tx_max && (skb_out->len % dev->maxpacket) == 0) *skb_put(skb_out, 1) = 0; /* force short packet */ /* set final frame length */ -- 2.39.2