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| author | Zi Shen Lim <zlim.lnx@gmail.com> | 2015-11-04 20:43:59 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-01-31 11:25:53 -0800 |
| commit | 3e34dfef4d71f81477a37d22e7a156cd840bd3fd (patch) | |
| tree | 296b923c344832f91b718779b2c8bd239f646117 | |
| parent | e905b2536e6ab51356b581a03b92832d6a05db65 (diff) | |
| download | lwn-3e34dfef4d71f81477a37d22e7a156cd840bd3fd.tar.gz lwn-3e34dfef4d71f81477a37d22e7a156cd840bd3fd.zip | |
arm64: bpf: fix mod-by-zero case
commit 14e589ff4aa3f28a5424e92b6495ecb8950080f7 upstream.
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 <zlim.lnx@gmail.com>
Reported-by: Yang Shi <yang.shi@linaro.org>
Reported-by: Xi Wang <xi.wang@gmail.com>
CC: Alexei Starovoitov <ast@plumgrid.com>
Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler")
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/arm64/net/bpf_jit_comp.c | 21 |
1 files changed, 13 insertions, 8 deletions
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); |