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Date: Tue, 10 Sep 2024 08:18:33 -0700
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Subject: Re: Kernel oops caused by signed divide
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To: Dave Thaler <dthaler1968@googlemail.com>,
 'Alexei Starovoitov' <alexei.starovoitov@gmail.com>,
 'Zac Ecob' <zacecob@protonmail.com>, 'Daniel Borkmann' <daniel@iogearbox.net>
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From: Yonghong Song <yonghong.song@linux.dev>
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On 9/10/24 7:44 AM, Dave Thaler wrote:
> Yonghong Song wrote:
> [...]
>> In verifier, we have
>>     /* [R,W]x div 0 -> 0 */
>>     /* [R,W]x mod 0 -> [R,W]x */
>>
>> What the value for
>>     Rx_a sdiv Rx_b -> ?
>> where Rx_a = INT64_MIN and Rx_b = -1?
>>
>> Should we just do
>>     INT64_MIN sdiv -1 -> -1
>> or some other values?
> What happens for BPF_NEG INT64_MIN?

Right. This is equivalent to INT64_MIN/-1. Indeed, we need check and protect for this case as well.