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[PATCH 3.14 05/25] skbuff: Fix skb checksum flag on skb pull

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

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

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

[ Upstream commit 6ae459bdaaeebc632b16e54dcbabb490c6931d61 ]

VXLAN device can receive skb with checksum partial. But the checksum
offset could be in outer header which is pulled on receive. This results
in negative checksum offset for the skb. Such skb can cause the assert
failure in skb_checksum_help(). Following patch fixes the bug by setting
checksum-none while pulling outer header.

Following is the kernel panic msg from old kernel hitting the bug.

------------[ cut here ]------------
kernel BUG at net/core/dev.c:1906!
RIP: 0010:[<ffffffff81518034>] skb_checksum_help+0x144/0x150
Call Trace:
<IRQ>
[<ffffffffa0164c28>] queue_userspace_packet+0x408/0x470 [openvswitch]
[<ffffffffa016614d>] ovs_dp_upcall+0x5d/0x60 [openvswitch]
[<ffffffffa0166236>] ovs_dp_process_packet_with_key+0xe6/0x100 [openvswitch]
[<ffffffffa016629b>] ovs_dp_process_received_packet+0x4b/0x80 [openvswitch]
[<ffffffffa016c51a>] ovs_vport_receive+0x2a/0x30 [openvswitch]
[<ffffffffa0171383>] vxlan_rcv+0x53/0x60 [openvswitch]
[<ffffffffa01734cb>] vxlan_udp_encap_recv+0x8b/0xf0 [openvswitch]
[<ffffffff8157addc>] udp_queue_rcv_skb+0x2dc/0x3b0
[<ffffffff8157b56f>] __udp4_lib_rcv+0x1cf/0x6c0
[<ffffffff8157ba7a>] udp_rcv+0x1a/0x20
[<ffffffff8154fdbd>] ip_local_deliver_finish+0xdd/0x280
[<ffffffff81550128>] ip_local_deliver+0x88/0x90
[<ffffffff8154fa7d>] ip_rcv_finish+0x10d/0x370
[<ffffffff81550365>] ip_rcv+0x235/0x300
[<ffffffff8151ba1d>] __netif_receive_skb+0x55d/0x620
[<ffffffff8151c360>] netif_receive_skb+0x80/0x90
[<ffffffff81459935>] virtnet_poll+0x555/0x6f0
[<ffffffff8151cd04>] net_rx_action+0x134/0x290
[<ffffffff810683d8>] __do_softirq+0xa8/0x210
[<ffffffff8162fe6c>] call_softirq+0x1c/0x30
[<ffffffff810161a5>] do_softirq+0x65/0xa0
[<ffffffff810687be>] irq_exit+0x8e/0xb0
[<ffffffff81630733>] do_IRQ+0x63/0xe0
[<ffffffff81625f2e>] common_interrupt+0x6e/0x6e

Reported-by: Anupam Chanda <achanda@vmware.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/skbuff.h |    3 +++
 1 file changed, 3 insertions(+)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2347,6 +2347,9 @@ 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->ip_summed = CHECKSUM_NONE;
 }
 
 unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);


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[PATCH 3.14 00/25] 3.14.56-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 02/25] af_unix: Convert the unix_sk macro to an inline function for type safety Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 24/25] sched/preempt: Rename PREEMPT_CHECK_OFFSET to PREEMPT_DISABLE_OFFSET Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 14/25] btrfs: fix use after free iterating extrefs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 06/25] skbuff: Fix skb checksum partial check. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 15/25] arm64: errata: use KBUILD_CFLAGS_MODULE for erratum #843419 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 16/25] i2c: rcar: enable RuntimePM before registering to the core Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 25/25] sched/preempt: Fix cond_resched_lock() and cond_resched_softirq() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 05/25] skbuff: Fix skb checksum flag on skb pull Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  [PATCH 3.14 09/25] ethtool: Use kcalloc instead of kmalloc for ethtool_get_strings Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-10-23 20:20 +0200
  Re: [PATCH 3.14 00/25] 3.14.56-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-10-23 23:10 +0200
  Re: [PATCH 3.14 00/25] 3.14.56-stable review Guenter Roeck <linux@roeck-us.net> - 2015-10-24 04:10 +0200

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