netdev - Re: [PATCH net] skbuff: Fix skb checksum flag on skb pull

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Date:	Mon, 31 Aug 2015 20:29:02 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] skbuff: Fix skb checksum flag on skb pull

On Mon, Aug 31, 2015 at 6:40 PM, Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
> On Mon, Aug 31, 2015 at 03:55:46PM -0700, Pravin B Shelar wrote:
>> VXLAN device can receive skb with checksum partial. But the checksum
>> offset could be in outer header which is pulled on receive. Such skb
>> can cause the panic when checksum is calculated on skb. Following patch
>> fixes the bug by setting checksum unnecessary while pulling outer header.
>>
>> ---8<---
>> [ 13.800141] RIP: 0010:[<ffffffff81518034>] [<ffffffff81518034>] skb_checksum_help+0x144/0x150
>> [ 13.800141] RSP: 0000:ffff88011fd83940 EFLAGS: 00010292
>> [ 13.800141] RAX: 0000000000000042 RBX: ffff880114dd56c0 RCX: ffff8801188d9580
>> ...
>> ...
>> [ 13.852308] Call Trace:
>> [ 13.852308] <IRQ>
>> [ 13.852308] [<ffffffffa0164c28>] queue_userspace_packet+0x408/0x470 [openvswitch]
>> [ 13.852308] [<ffffffffa016614d>] ovs_dp_upcall+0x5d/0x60 [openvswitch]
>> [ 13.852308] [<ffffffffa0166236>] ovs_dp_process_packet_with_key+0xe6/0x100 [openvswitch]
>> [ 13.852308] [<ffffffffa016629b>] ovs_dp_process_received_packet+0x4b/0x80 [openvswitch]
>
> that doesn't look like upstream kernel.
> The above two functions don't exist in net-next.
>

Bug was reported on older kernel. But the issue exist on net-next
kernel. For example when vxlan checksum is turned on.
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