linux-kernel - [PATCH AUTOSEL for 4.9 018/281] net: cdc

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Date:   Mon, 19 Mar 2018 15:58:10 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Jim Baxter <jim_baxter@...tor.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.9 018/281] net: cdc_ncm: Fix TX zero padding

From: Jim Baxter <jim_baxter@...tor.com>

[ Upstream commit aeca3a77b1e0ed06a095933b89c86aed007383eb ]

The zero padding that is added to NTB's does
not zero the memory correctly.
This is because the skb_put modifies the value
of skb_out->len which results in the memset
command not setting any memory to zero as
(ctx->tx_max - skb_out->len) == 0.

I have resolved this by storing the size of
the memory to be zeroed before the skb_put
and using this in the memset call.

Signed-off-by: Jim Baxter <jim_baxter@...tor.com>
Reviewed-by: Bjørn Mork <bjorn@...k.no>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 drivers/net/usb/cdc_ncm.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index dc6d3b0a0be8..feb61eaffe32 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1118,6 +1118,7 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 	u16 n = 0, index, ndplen;
 	u8 ready2send = 0;
 	u32 delayed_ndp_size;
+	size_t padding_count;
 
 	/* When our NDP gets written in cdc_ncm_ndp(), then skb_out->len gets updated
 	 * accordingly. Otherwise, we should check here.
@@ -1274,11 +1275,13 @@ cdc_ncm_fill_tx_frame(struct usbnet *dev, struct sk_buff *skb, __le32 sign)
 	 * a ZLP after full sized NTBs.
 	 */
 	if (!(dev->driver_info->flags & FLAG_SEND_ZLP) &&
-	    skb_out->len > ctx->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 < ctx->tx_max && (skb_out->len % dev->maxpacket) == 0)
+	    skb_out->len > ctx->min_tx_pkt) {
+		padding_count = ctx->tx_max - skb_out->len;
+		memset(skb_put(skb_out, padding_count), 0, padding_count);
+	} 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 */
 	nth16 = (struct usb_cdc_ncm_nth16 *)skb_out->data;
-- 
2.14.1