| Message ID | 1452015244-1230-1-git-send-email-rabin@rab.in (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Jan 05, 2016 at 06:34:04PM +0100, Rabin Vincent wrote: > 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 <rabin@rab.in> Looks good as a fix for classic jit. For eBPF we would want to check this in verifier. Acked-by: Alexei Starovoitov <ast@kernel.org>
From: Rabin Vincent <rabin@rab.in> Date: Tue, 5 Jan 2016 18:34:04 +0100 > 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 <rabin@rab.in> Applied, thanks.
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);
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 <rabin@rab.in> --- arch/arm/net/bpf_jit_32.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)