RE: [RFC] networking: convert many more places to skb_put_zero()

-----Original Message-----
From: Johannes Berg [mailto:johannes@sipsolutions.net]
Sent: Thursday, June 15, 2017 2:58 PM
To: YUAN Linyu; netdev@vger.kernel.org
Subject: Re: [RFC] networking: convert many more places to skb_put_zero()

On Thu, 2017-06-15 at 00:23 +0000, YUAN Linyu wrote:

quoted

Hi,
Indeed, it find more.
Compare with my patch, still lost pattern like below,
1. sctp and openvswitch

--- a/net/sctp/output.c
+++ b/net/sctp/output.c

@@ -463,7 +463,7 @@ static int sctp_packet_pack(struct sctp_packet

*packet,

 			padding = SCTP_PAD4(chunk->skb->len) -
chunk->skb->len;
 			if (padding)
-				memset(skb_put(chunk->skb, padding),
0, padding);
+				skb_put_zero(chunk->skb, padding);

Yep, good catch, this finds 18 instances thereof:

@@
expression skb, len;
@@
-memset(skb_put(skb, len), 0, len);
+skb_put_zero(skb, len);

quoted

--- a/net/dsa/tag_trailer.c
+++ b/net/dsa/tag_trailer.c

@@ -43,8 +43,7 @@ static struct sk_buff *trailer_xmit(struct sk_buff

*skb, struct net_device *dev)
 	kfree_skb(skb);

 	if (padlen) {
-		u8 *pad = skb_put(nskb, padlen);
-		memset(pad, 0, padlen);
+		skb_put_zero(nskb, padlen);

I'd have thought it finds this, but indeed it doesn't; there's only one
instances this changes though:

@@
type t;
expression skb, len;
identifier p;
@@
t *p
- = skb_put(skb, len);
+ = skb_put_zero(skb, len);
-memset(p, 0, len);

and it can't figure out that it should remove the variable, without
much more work that's not really worth it for one instance :)

Yes, I agree, 
it conflict with previous spatch which will keep "pad" variable, right?

I can do it by hand if spatch not work

johannes