[PATCH bpf-next v4 04/10] bpf: remove never-hit branches in verifier adjust_scalar_min_max_vals

[Yonghong Song]

In verifier function adjust_scalar_min_max_vals,
when src_known is false and the opcode is BPF_LSH/BPF_RSH,
early return will happen in the function. So remove
the branch in handling BPF_LSH/BPF_RSH when src_known is false.

Signed-off-by: Yonghong Song <y...@fb.com>
---
 kernel/bpf/verifier.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d00bf53..1bbb43d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2932,10 +2932,7 @@ static int adjust_scalar_min_max_vals(struct 
bpf_verifier_env *env,
                        dst_reg->umin_value <<= umin_val;
                        dst_reg->umax_value <<= umax_val;
                }
-               if (src_known)
-                       dst_reg->var_off = tnum_lshift(dst_reg->var_off, 
umin_val);
-               else
-                       dst_reg->var_off = tnum_lshift(tnum_unknown, umin_val);
+               dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
                /* We may learn something more from the var_off */
                __update_reg_bounds(dst_reg);
                break;
@@ -2963,11 +2960,7 @@ static int adjust_scalar_min_max_vals(struct 
bpf_verifier_env *env,
                 */
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
-               if (src_known)
-                       dst_reg->var_off = tnum_rshift(dst_reg->var_off,
-                                                      umin_val);
-               else
-                       dst_reg->var_off = tnum_rshift(tnum_unknown, umin_val);
+               dst_reg->var_off = tnum_rshift(dst_reg->var_off, umin_val);
                dst_reg->umin_value >>= umax_val;
                dst_reg->umax_value >>= umin_val;
                /* We may learn something more from the var_off */
-- 
2.9.5