[PATCH AUTOSEL for 4.4 012/167] net: cdc_ncm: Fix TX zero padding

Sasha Levin
2018-03-19T16:07:05Z

From: Jim Baxter <jim_baxter@mentor.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@mentor.com>
Reviewed-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.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 72cb30828a12..c8e98c8e29fa 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1069,6 +1069,7 @@ 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.
@@ -1225,11 +1226,13 @@ 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