linux-kernel - Re: Linux 4.4.34

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Message-ID: <CANn89iKZMcnzLJUNE286pBKSaL3kcrBgwpdihxSMm8Ze5L_-qw@mail.gmail.com>
Date:   Tue, 22 Nov 2016 09:56:34 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Andre Noll <maan@...bingen.mpg.de>
Cc:     "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "willemb@...gle.com" <willemb@...gle.com>,
        "jslaby@...e.cz" <jslaby@...e.cz>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "yibyang@...co.com" <yibyang@...co.com>
Subject: Re: Linux 4.4.34

On Tue, Nov 22, 2016 at 9:55 AM, Andre Noll <maan@...bingen.mpg.de> wrote:
> On Tue, Nov 22, 09:46, Eric Dumazet wrote
>> This is an aliasing problem.
>> Tom code is hard to read and understand.
>>
>> Andre, could you try :
>>
>> diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
>> index 69e4463a4b1b..b045980faaea 100644
>> --- a/net/core/flow_dissector.c
>> +++ b/net/core/flow_dissector.c
>> @@ -157,6 +157,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
>>                 memcpy(key_eth_addrs, &eth->h_dest, sizeof(*key_eth_addrs));
>>         }
>>
>> +       barrier();
>>  again:
>>         switch (proto) {
>>         case htons(ETH_P_IP): {
>
> This patch on top of v4.4.34 makes no difference: I'm still getting
> the panic in eth_type_trans().
>

What compiler are you using exactly ?

Please try :

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 69e4463a4b1b..48791f372aa2 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -551,6 +551,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,

        key_control->thoff = (u16)nhoff;
 out:
+       barrier();
        key_basic->n_proto = proto;
        key_basic->ip_proto = ip_proto;