| From 251599e1d6906621f49218d7b474ddd159e58f3b Mon Sep 17 00:00:00 2001 |
| From: Zi Shen Lim <zlim.lnx@gmail.com> |
| Date: Tue, 3 Nov 2015 22:56:44 -0800 |
| Subject: arm64: bpf: fix div-by-zero case |
| |
| From: Zi Shen Lim <zlim.lnx@gmail.com> |
| |
| commit 251599e1d6906621f49218d7b474ddd159e58f3b upstream. |
| |
| In the case of division by zero in a BPF program: |
| A = A / X; (X == 0) |
| the expected behavior is to terminate with return value 0. |
| |
| This is confirmed by the test case introduced in commit 86bf1721b226 |
| ("test_bpf: add tests checking that JIT/interpreter sets A and X to 0."). |
| |
| Reported-by: Yang Shi <yang.shi@linaro.org> |
| Tested-by: Yang Shi <yang.shi@linaro.org> |
| CC: Xi Wang <xi.wang@gmail.com> |
| CC: Alexei Starovoitov <ast@plumgrid.com> |
| CC: linux-arm-kernel@lists.infradead.org |
| CC: linux-kernel@vger.kernel.org |
| Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") |
| Signed-off-by: Zi Shen Lim <zlim.lnx@gmail.com> |
| Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/arm64/net/bpf_jit.h | 3 ++- |
| arch/arm64/net/bpf_jit_comp.c | 37 +++++++++++++++++++++++++------------ |
| 2 files changed, 27 insertions(+), 13 deletions(-) |
| |
| --- a/arch/arm64/net/bpf_jit.h |
| +++ b/arch/arm64/net/bpf_jit.h |
| @@ -1,7 +1,7 @@ |
| /* |
| * BPF JIT compiler for ARM64 |
| * |
| - * Copyright (C) 2014 Zi Shen Lim <zlim.lnx@gmail.com> |
| + * Copyright (C) 2014-2015 Zi Shen Lim <zlim.lnx@gmail.com> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| @@ -35,6 +35,7 @@ |
| aarch64_insn_gen_comp_branch_imm(0, offset, Rt, A64_VARIANT(sf), \ |
| AARCH64_INSN_BRANCH_COMP_##type) |
| #define A64_CBZ(sf, Rt, imm19) A64_COMP_BRANCH(sf, Rt, (imm19) << 2, ZERO) |
| +#define A64_CBNZ(sf, Rt, imm19) A64_COMP_BRANCH(sf, Rt, (imm19) << 2, NONZERO) |
| |
| /* Conditional branch (immediate) */ |
| #define A64_COND_BRANCH(cond, offset) \ |
| --- a/arch/arm64/net/bpf_jit_comp.c |
| +++ b/arch/arm64/net/bpf_jit_comp.c |
| @@ -1,7 +1,7 @@ |
| /* |
| * BPF JIT compiler for ARM64 |
| * |
| - * Copyright (C) 2014 Zi Shen Lim <zlim.lnx@gmail.com> |
| + * Copyright (C) 2014-2015 Zi Shen Lim <zlim.lnx@gmail.com> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| @@ -225,6 +225,17 @@ static int build_insn(const struct bpf_i |
| u8 jmp_cond; |
| s32 jmp_offset; |
| |
| +#define check_imm(bits, imm) do { \ |
| + if ((((imm) > 0) && ((imm) >> (bits))) || \ |
| + (((imm) < 0) && (~(imm) >> (bits)))) { \ |
| + pr_info("[%2d] imm=%d(0x%x) out of range\n", \ |
| + i, imm, imm); \ |
| + return -EINVAL; \ |
| + } \ |
| +} while (0) |
| +#define check_imm19(imm) check_imm(19, imm) |
| +#define check_imm26(imm) check_imm(26, imm) |
| + |
| switch (code) { |
| /* dst = src */ |
| case BPF_ALU | BPF_MOV | BPF_X: |
| @@ -258,8 +269,21 @@ static int build_insn(const struct bpf_i |
| break; |
| 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: |
| ctx->tmp_used = 1; |
| @@ -393,17 +417,6 @@ emit_bswap_uxt: |
| emit(A64_ASR(is64, dst, dst, imm), ctx); |
| break; |
| |
| -#define check_imm(bits, imm) do { \ |
| - if ((((imm) > 0) && ((imm) >> (bits))) || \ |
| - (((imm) < 0) && (~(imm) >> (bits)))) { \ |
| - pr_info("[%2d] imm=%d(0x%x) out of range\n", \ |
| - i, imm, imm); \ |
| - return -EINVAL; \ |
| - } \ |
| -} while (0) |
| -#define check_imm19(imm) check_imm(19, imm) |
| -#define check_imm26(imm) check_imm(26, imm) |
| - |
| /* JUMP off */ |
| case BPF_JMP | BPF_JA: |
| jmp_offset = bpf2a64_offset(i + off, i, ctx); |