From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965577AbbKEEoI (ORCPT ); Wed, 4 Nov 2015 23:44:08 -0500 Received: from mail-pa0-f44.google.com ([209.85.220.44]:34324 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754063AbbKEEoF (ORCPT ); Wed, 4 Nov 2015 23:44:05 -0500 From: Zi Shen Lim To: Catalin Marinas , Alexei Starovoitov Cc: Zi Shen Lim , Yang Shi , Xi Wang , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Subject: [PATCH] arm64: bpf: fix mod-by-zero case Date: Wed, 4 Nov 2015 20:43:59 -0800 Message-Id: <1446698639-12362-1-git-send-email-zlim.lnx@gmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Turns out in the case of modulo by zero in a BPF program: A = A % X; (X == 0) the expected behavior is to terminate with return value 0. The bug in JIT is exposed by a new test case [1]. [1] https://lkml.org/lkml/2015/11/4/499 Signed-off-by: Zi Shen Lim Reported-by: Yang Shi Reported-by: Xi Wang CC: Alexei Starovoitov CC: Catalin Marinas Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") Cc: # 3.18+ --- This patch applies on top of "arm64: bpf: fix fiv-by-zero case" [2]. [2] https://lkml.org/lkml/2015/11/4/25 arch/arm64/net/bpf_jit_comp.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 9ae6f23..6217f80 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -269,6 +269,8 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) break; case BPF_ALU | BPF_DIV | BPF_X: case BPF_ALU64 | BPF_DIV | BPF_X: + case BPF_ALU | BPF_MOD | BPF_X: + case BPF_ALU64 | BPF_MOD | BPF_X: { const u8 r0 = bpf2a64[BPF_REG_0]; @@ -281,16 +283,19 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) check_imm26(jmp_offset); emit(A64_B(jmp_offset), ctx); /* else */ - emit(A64_UDIV(is64, dst, dst, src), ctx); + switch (BPF_OP(code)) { + case BPF_DIV: + emit(A64_UDIV(is64, dst, dst, src), ctx); + break; + case BPF_MOD: + ctx->tmp_used = 1; + emit(A64_UDIV(is64, tmp, dst, src), ctx); + emit(A64_MUL(is64, tmp, tmp, src), ctx); + emit(A64_SUB(is64, dst, dst, tmp), ctx); + break; + } break; } - case BPF_ALU | BPF_MOD | BPF_X: - case BPF_ALU64 | BPF_MOD | BPF_X: - ctx->tmp_used = 1; - emit(A64_UDIV(is64, tmp, dst, src), ctx); - emit(A64_MUL(is64, tmp, tmp, src), ctx); - emit(A64_SUB(is64, dst, dst, tmp), ctx); - break; case BPF_ALU | BPF_LSH | BPF_X: case BPF_ALU64 | BPF_LSH | BPF_X: emit(A64_LSLV(is64, dst, dst, src), ctx); -- 1.9.1