Re: [PATCH] net: exit immediately when encounter ipv6 fragment in skb_checksum_setup_ipv6()

[David Miller]

From: Miaohe Lin 
Date: Thu, 27 Aug 2020 07:21:59 -0400

> skb_checksum_setup_ipv6() always return -EPROTO if ipv6 packet is fragment.
> So we should not continue to parse other header type in this case. Also
> remove unnecessary local variable 'fragment'.
> 
> Signed-off-by: Miaohe Lin 

Again, this optimization is arguable at best.  The code functions fine and
correctly as-is.

I'm not applying this, sorry.

[PATCH] net: exit immediately when encounter ipv6 fragment in skb_checksum_setup_ipv6()

[Miaohe Lin]

skb_checksum_setup_ipv6() always return -EPROTO if ipv6 packet is fragment.
So we should not continue to parse other header type in this case. Also
remove unnecessary local variable 'fragment'.

Signed-off-by: Miaohe Lin 
---
 net/core/skbuff.c | 12 ++--
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c3496bd8e99e..4dc92290becd 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4894,11 +4894,9 @@ static int skb_checksum_setup_ipv6(struct sk_buff *skb, 
bool recalculate)
u8 nexthdr;
unsigned int off;
unsigned int len;
-   bool fragment;
bool done;
__sum16 *csum;
 
-   fragment = false;
done = false;
 
off = sizeof(struct ipv6hdr);
@@ -4956,8 +4954,11 @@ static int skb_checksum_setup_ipv6(struct sk_buff *skb, 
bool recalculate)
 
hp = OPT_HDR(struct frag_hdr, skb, off);
 
-   if (hp->frag_off & htons(IP6_OFFSET | IP6_MF))
-   fragment = true;
+   /* Exit immediately when encounter ipv6 fragment. */
+   if (hp->frag_off & htons(IP6_OFFSET | IP6_MF)) {
+   err = -EPROTO;
+   goto out;
+   }
 
nexthdr = hp->nexthdr;
off += sizeof(struct frag_hdr);
@@ -4970,8 +4971,7 @@ static int skb_checksum_setup_ipv6(struct sk_buff *skb, 
bool recalculate)
}
 
err = -EPROTO;
-
-   if (!done || fragment)
+   if (!done)
goto out;
 
csum = skb_checksum_setup_ip(skb, nexthdr, off);
-- 
2.19.1