[3.19.y-ckt stable] Patch "skbuff: Fix skb checksum partial check." has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    skbuff: Fix skb checksum partial check.

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt10.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From d7f1768d0f8350632c3a84728f764fe8f18e5014 Mon Sep 17 00:00:00 2001
From: Pravin B Shelar <pshelar at nicira.com>
Date: Mon, 28 Sep 2015 17:24:25 -0700
Subject: [PATCH 057/120] skbuff: Fix skb checksum partial check.

[ Upstream commit 31b33dfb0a144469dd805514c9e63f4993729a48 ]

Earlier patch 6ae459bda tried to detect void ckecksum partial
skb by comparing pull length to checksum offset. But it does
not work for all cases since checksum-offset depends on
updates to skb->data.

Following patch fixes it by validating checksum start offset
after skb-data pointer is updated. Negative value of checksum
offset start means there is no need to checksum.

Fixes: 6ae459bda ("skbuff: Fix skb checksum flag on skb pull")
Reported-by: Andrew Vagin <avagin at odin.com>
Signed-off-by: Pravin B Shelar <pshelar at nicira.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 include/linux/skbuff.h | 2 +-
 net/core/skbuff.c      | 9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8271178..b0e064e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2576,7 +2576,7 @@ static inline void skb_postpull_rcsum(struct sk_buff *skb,
 	if (skb->ip_summed == CHECKSUM_COMPLETE)
 		skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
 	else if (skb->ip_summed == CHECKSUM_PARTIAL &&
-		 skb_checksum_start_offset(skb) <= len)
+		 skb_checksum_start_offset(skb) < 0)
 		skb->ip_summed = CHECKSUM_NONE;
 }

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 0998af7..ce3b085 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2979,11 +2979,12 @@ EXPORT_SYMBOL(skb_append_datato_frags);
  */
 unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
 {
+	unsigned char *data = skb->data;
+
 	BUG_ON(len > skb->len);
-	skb->len -= len;
-	BUG_ON(skb->len < skb->data_len);
-	skb_postpull_rcsum(skb, skb->data, len);
-	return skb->data += len;
+	__skb_pull(skb, len);
+	skb_postpull_rcsum(skb, data, len);
+	return skb->data;
 }
 EXPORT_SYMBOL_GPL(skb_pull_rcsum);

--
1.9.1