diff mbox series

[bpf-next,v7,04/10] bpf: remove never-hit branches in verifier adjust_scalar_min_max_vals

Message ID 20180425192910.556352-5-yhs@fb.com
State Changes Requested, archived
Delegated to: BPF Maintainers
Headers show
Series bpf: add bpf_get_stack helper | expand

Commit Message

Yonghong Song April 25, 2018, 7:29 p.m. UTC 
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 <yhs@fb.com>
---
 kernel/bpf/verifier.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

Comments

Alexei Starovoitov April 27, 2018, 11:24 p.m. UTC | #1 
On Wed, Apr 25, 2018 at 12:29:04PM -0700, Yonghong Song wrote:
> 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 <yhs@fb.com>

Acked-by: Alexei Starovoitov <ast@kernel.org>
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 988400e..6e3f859 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2940,10 +2940,7 @@  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;
@@ -2971,11 +2968,7 @@  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 */