linux-kernel - Re: [PATCH] arm64: bpf: fix div-by-zero case

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Message-ID: <563A4C9A.7000002@linaro.org>
Date:	Wed, 04 Nov 2015 10:21:14 -0800
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Xi Wang <xi.wang@...il.com>, Zi Shen Lim <zlim.lnx@...il.com>
CC:	Catalin Marinas <catalin.marinas@....com>, stable@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Alexei Starovoitov <ast@...mgrid.com>
Subject: Re: [PATCH] arm64: bpf: fix div-by-zero case

On 11/3/2015 11:04 PM, Xi Wang wrote:
> On Tue, Nov 3, 2015 at 10:56 PM, Zi Shen Lim <zlim.lnx@...il.com> wrote:
>>          case BPF_ALU | BPF_DIV | BPF_X:
>>          case BPF_ALU64 | BPF_DIV | BPF_X:
>> +       {
>> +               const u8 r0 = bpf2a64[BPF_REG_0];
>> +
>> +               /* if (src == 0) return 0 */
>> +               jmp_offset = 3; /* skip ahead to else path */
>> +               check_imm19(jmp_offset);
>> +               emit(A64_CBNZ(is64, src, jmp_offset), ctx);
>> +               emit(A64_MOVZ(1, r0, 0, 0), ctx);
>> +               jmp_offset = epilogue_offset(ctx);
>> +               check_imm26(jmp_offset);
>> +               emit(A64_B(jmp_offset), ctx);
>> +               /* else */
>>                  emit(A64_UDIV(is64, dst, dst, src), ctx);
>>                  break;
>> +       }
>>          case BPF_ALU | BPF_MOD | BPF_X:
>>          case BPF_ALU64 | BPF_MOD | BPF_X:
>
> BPF_MOD might need the same fix.

Agreed, and we may need add one more test cases in test_bpf module to 
cover MOD?

Yang

>
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> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>

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