From 14e589ff4aa3f28a5424e92b6495ecb8950080f7 Mon Sep 17 00:00:00 2001 From: Zi Shen Lim Date: Wed, 4 Nov 2015 20:43:59 -0800 Subject: arm64: bpf: fix mod-by-zero case 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 Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") Cc: # 3.18+ Signed-off-by: Catalin Marinas --- arch/arm64/net/bpf_jit_comp.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) (limited to 'arch') diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 9ae6f2373a6d..6217f80702d2 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); -- cgit v1.2.3-59-g8ed1b