netdev - Re: UBSAN reports issue in ip_idents

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Message-ID: <20160920162525.GM1843@nanopsycho.orion>
Date:   Tue, 20 Sep 2016 18:25:25 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: UBSAN reports issue in ip_idents_reserve

Tue, Sep 20, 2016 at 05:25:16PM CEST, eric.dumazet@...il.com wrote:
>On Tue, 2016-09-20 at 07:11 -0700, Eric Dumazet wrote:
>> On Tue, 2016-09-20 at 15:39 +0200, Jiri Pirko wrote:
>> 
>> > I see. So how to silent the warning?
>> > 
>> 
>> We can replace the atomic_add_return() and use a loop around
>> atomic_read() and atomic_cmpxhg()
>> 
>> This would change the nice property of x86 xadd into a loop.
>> 
>> Or we also could fallback to random generation if the atomic_cmpxchg()
>> fails.
>> 
>> I'll provide a patch, thanks.
>> 

I'm going to test your patch now.

>
>I looks at other places, I am surprised you do not see other UBSAN
>issues in networking :)

Not yet :)

>
>netdev_refcnt_read() can potentially gives errors as well.
>
>
>