* [PATCH V2 0/1] net: cdc_ncm: Fix TX zero padding
@ 2017-05-08 12:49 Jim Baxter
2017-05-08 12:49 ` [PATCH V2 1/1] " Jim Baxter
0 siblings, 1 reply; 3+ messages in thread
From: Jim Baxter @ 2017-05-08 12:49 UTC (permalink / raw)
To: linux-usb, netdev, linux-kernel, Oliver Neukum; +Cc: jim_baxter
Analysis
--------
The zero padding that is added to NTB's does not zero
the memory correctly.
This happens because the skb_put called within the memset in
the line:
memset(skb_put(skb_out, ctx->tx_max - skb_out->len),
0, ctx->tx_max - skb_out->len);
causes the value of skb_out->len to be modified during
the two uses of it within the above line.
This causes non-zeroed data at the end of skb_out.
This issue was found when connecting between an ARM
Sabre SD Host platform and a test box that was
dropping the NDP's due to the non zeroed memory being
identified as an error.
Solution
--------
To resolve this I have cached the value of
ctx->tx_max - skb_out->len before the memset operation.
----
V1: Sent to linux-use for review.
V2: Added netdev mailing list as it was missed for V1.
Jim Baxter (1):
net: cdc_ncm: Fix TX zero padding
drivers/net/usb/cdc_ncm.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--
1.9.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH V2 1/1] net: cdc_ncm: Fix TX zero padding
2017-05-08 12:49 [PATCH V2 0/1] net: cdc_ncm: Fix TX zero padding Jim Baxter
@ 2017-05-08 12:49 ` Jim Baxter
2017-05-08 20:01 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Jim Baxter @ 2017-05-08 12:49 UTC (permalink / raw)
To: linux-usb, netdev, linux-kernel, Oliver Neukum; +Cc: jim_baxter
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>
---
V1: Sent to linux-use for review.
V2: Added netdev mailing list as it was missed for V1.
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 f317984..e2a48d7 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -1087,6 +1087,7 @@ struct sk_buff *
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.
@@ -1243,11 +1244,13 @@ struct sk_buff *
* 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;
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH V2 1/1] net: cdc_ncm: Fix TX zero padding
2017-05-08 12:49 ` [PATCH V2 1/1] " Jim Baxter
@ 2017-05-08 20:01 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2017-05-08 20:01 UTC (permalink / raw)
To: jim_baxter; +Cc: linux-usb, netdev, linux-kernel, oliver
From: Jim Baxter <jim_baxter@mentor.com>
Date: Mon, 8 May 2017 13:49:57 +0100
> 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>
Applied, thank you.
^ permalink raw reply [flat|nested] 3+ messages in thread
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