From f941461c925832fbeb7876b794ab9fbec6a7a8af Mon Sep 17 00:00:00 2001 From: Rabin Vincent Date: Tue, 5 Jan 2016 18:34:04 +0100 Subject: [PATCH] ARM: net: bpf: fix zero right shift The LSR instruction cannot be used to perform a zero right shift since a 0 as the immediate value (imm5) in the LSR instruction encoding means that a shift of 32 is perfomed. See DecodeIMMShift() in the ARM ARM. Make the JIT skip generation of the LSR if a zero-shift is requested. This was found using american fuzzy lop. Signed-off-by: Rabin Vincent Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- arch/arm/net/bpf_jit_32.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index e153eb065fe4..93d0b6d0b63e 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -756,7 +756,8 @@ load_ind: case BPF_ALU | BPF_RSH | BPF_K: if (unlikely(k > 31)) return -1; - emit(ARM_LSR_I(r_A, r_A, k), ctx); + if (k) + emit(ARM_LSR_I(r_A, r_A, k), ctx); break; case BPF_ALU | BPF_RSH | BPF_X: update_on_xread(ctx); -- 2.39.2