[PATCH bpf-next v5 1/6] bpf/verifier: replace calls to mark_reg_unknown.

[Cupertino Miranda <cupertino.miranda@xxxxxxxxxx>]

In order to further simplify the code in adjust_scalar_min_max_vals all
the calls to mark_reg_unknown are replaced by __mark_reg_unknown.

static void mark_reg_unknown(struct bpf_verifier_env *env,
  			     struct bpf_reg_state *regs, u32 regno)
{
	if (WARN_ON(regno >= MAX_BPF_REG)) {
		... mark all regs not init ...
		return;
    }
	__mark_reg_unknown(env, regs + regno);
}

The 'regno >= MAX_BPF_REG' does not apply to
adjust_scalar_min_max_vals(), because it is only called from the
following stack:
  - check_alu_op
    - adjust_reg_min_max_vals
      - adjust_scalar_min_max_vals

The check_alu_op() does check_reg_arg() which verifies that both src and
dst register numbers are within bounds.

Signed-off-by: Cupertino Miranda <cupertino.miranda@xxxxxxxxxx>
Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
Cc: Yonghong Song <yonghong.song@xxxxxxxxx>
Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Cc: David Faust <david.faust@xxxxxxxxxx>
Cc: Jose Marchesi <jose.marchesi@xxxxxxxxxx>
Cc: Elena Zannoni <elena.zannoni@xxxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
---
 kernel/bpf/verifier.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7360f04f9ec7..41c66cc6db80 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13887,7 +13887,6 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 				      struct bpf_reg_state *dst_reg,
 				      struct bpf_reg_state src_reg)
 {
-	struct bpf_reg_state *regs = cur_regs(env);
 	u8 opcode = BPF_OP(insn->code);
 	bool src_known;
 	s64 smin_val, smax_val;
@@ -13994,7 +13993,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 			/* Shifts greater than 31 or 63 are undefined.
 			 * This includes shifts by a negative number.
 			 */
-			mark_reg_unknown(env, regs, insn->dst_reg);
+			__mark_reg_unknown(env, dst_reg);
 			break;
 		}
 		if (alu32)
@@ -14007,7 +14006,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 			/* Shifts greater than 31 or 63 are undefined.
 			 * This includes shifts by a negative number.
 			 */
-			mark_reg_unknown(env, regs, insn->dst_reg);
+			__mark_reg_unknown(env, dst_reg);
 			break;
 		}
 		if (alu32)
@@ -14020,7 +14019,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 			/* Shifts greater than 31 or 63 are undefined.
 			 * This includes shifts by a negative number.
 			 */
-			mark_reg_unknown(env, regs, insn->dst_reg);
+			__mark_reg_unknown(env, dst_reg);
 			break;
 		}
 		if (alu32)
@@ -14029,7 +14028,7 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 			scalar_min_max_arsh(dst_reg, &src_reg);
 		break;
 	default:
-		mark_reg_unknown(env, regs, insn->dst_reg);
+		__mark_reg_unknown(env, dst_reg);
 		break;
 	}
 
-- 
2.39.2