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[PATCH 4.1 04/46] skbuff: Fix skb checksum partial check.

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4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pravin B Shelar <pshelar@nicira.com>

[ 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@odin.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/skbuff.h |    2 +-
 net/core/skbuff.c      |    9 +++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2589,7 +2589,7 @@ static inline void skb_postpull_rcsum(st
 	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;
 }
 
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2976,11 +2976,12 @@ 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);
 


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[PATCH 4.1 00/46] 4.1.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 05/46] inet: fix races in reqsk_queue_hash_req() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 06/46] net: add pfmemalloc check in sk_add_backlog() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 04/46] skbuff: Fix skb checksum partial check. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 02/46] l2tp: protect tunnel->del_work by ref_count Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 16/46] af_unix: return data from multiple SKBs on recv() with MSG_PEEK flag Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 30/46] i2c: designware-platdrv: enable RuntimePM before registering to the core Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 29/46] i2c: designware: Do not use parameters from ACPI on Dell Inspiron 7348 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 34/46] drm/radeon: attach tile property to mst connector Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 17/46] net/unix: fix logic about sk_peek_offset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 32/46] drm/nouveau/fbcon: take runpm reference when userspace has an open fd Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 09/46] bpf: fix panic in SO_GET_FILTER with native ebpf programs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 27/46] i2c: rcar: enable RuntimePM before registering to the core Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 31/46] workqueue: make sure delayed work run in local cpu Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
  [PATCH 4.1 39/46] sched/preempt: Fix cond_resched_lock() and cond_resched_softirq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:10 +0200
    Re: [PATCH 4.1 39/46] sched/preempt: Fix cond_resched_lock() and  cond_resched_softirq() Thomas Backlund <backlund.thomas@gmail.com> - 2015-10-23 22:20 +0200
      Re: [PATCH 4.1 39/46] sched/preempt: Fix cond_resched_lock() and  cond_resched_softirq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-24 01:30 +0200
  Re: [PATCH 4.1 00/46] 4.1.12-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-10-23 22:40 +0200
    Re: [PATCH 4.1 00/46] 4.1.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-24 01:30 +0200
      Re: [PATCH 4.1 00/46] 4.1.12-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-24 03:20 +0200
  Re: [PATCH 4.1 00/46] 4.1.12-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-24 05:20 +0200
    Re: [PATCH 4.1 00/46] 4.1.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-24 15:30 +0200

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