netdev - Re: [PATCH net] net: increment xmit_recursion level in dev_direct

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Message-ID: <363832b8-1d7e-1e9e-8887-ef97d748b0c7@gmail.com>
Date:   Thu, 18 Jun 2020 21:42:16 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>, edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com, kuba@...nel.org,
        syzkaller@...glegroups.com
Subject: Re: [PATCH net] net: increment xmit_recursion level in
 dev_direct_xmit()



On 6/18/20 8:48 PM, David Miller wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> Date: Wed, 17 Jun 2020 22:23:25 -0700
> 
>> Back in commit f60e5990d9c1 ("ipv6: protect skb->sk accesses
>> from recursive dereference inside the stack") Hannes added code
>> so that IPv6 stack would not trust skb->sk for typical cases
>> where packet goes through 'standard' xmit path (__dev_queue_xmit())
>>
>> Alas af_packet had a dev_direct_xmit() path that was not
>> dealing yet with xmit_recursion level.
>>
>> Also change sk_mc_loop() to dump a stack once only.
>>
>> Without this patch, syzbot was able to trigger :
>  ...
>> f60e5990d9c1 ("ipv6: protect skb->sk accesses from recursive dereference inside the stack")
>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>> Reported-by: syzbot <syzkaller@...glegroups.com>
> 
> Applied and queued up for -stable.
> 
> I only noticed after pushing this out the missing "Fixes: " prefix, but not
> much I can do about this now sorry :-/

Oh right, sorry for this.