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Subject: Re: [net] a6211caa63:
 dmesg.UBSAN:signed-integer-overflow_in_arch/x86/include/asm/atomic.h
To:     Peter Zijlstra <peterz@infradead.org>,
        Eric Dumazet <edumazet@google.com>
Cc:     Yuqi Jin <jinyuqi@huawei.com>,
        "David S. Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Jiri Pirko <jiri@resnulli.us>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Jiong Wang <jiongwang@huawei.com>,
        Shaokun Zhang <zhangshaokun@hisilicon.com>,
        LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org
References: <20200605080929.GK12456@shao2-debian>
 <CANn89iK1EfAqw-SkXyQR=88fKnBpXCcR_FaiFkVDUNazNgAX1g@mail.gmail.com>
 <20200605140521.GD4117@hirez.programming.kicks-ass.net>
From:   "Chen, Rong A" <rong.a.chen@intel.com>
Message-ID: <a33f477a-3847-f870-bf3f-845910b90665@intel.com>
Date:   Sat, 6 Jun 2020 11:03:13 +0800
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On 6/5/2020 10:05 PM, Peter Zijlstra wrote:
> On Fri, Jun 05, 2020 at 06:17:51AM -0700, Eric Dumazet wrote:
>> On Fri, Jun 5, 2020 at 1:10 AM kernel test robot <rong.a.chen@intel.com> wrote:
>> There you go.
>>
>> We decided this was a bogus report, and that UBSAN requires sane compilers.
>>
>> Please read the fine comment that was added in this commit and update
>> your compiler or do not mess with compiler flags.
>>
>> +       /* If UBSAN reports an error there, please make sure your compiler
>> +        * supports -fno-strict-overflow before reporting it that was a bug
>> +        * in UBSAN, and it has been fixed in GCC-8.
>> +        */
>> +       return atomic_add_return(segs + delta, p_id) - segs;
>>>          make HOSTCC=gcc-4.9 CC=gcc-4.9 ARCH=i386 olddefconfig prepare modules_prepare bzImage
> Rong, can you make sure to exclude gcc<8 for UBSAN reports ?

Got it, thank's for your warning.

Best Regards,
Rong Chen