netdev - [PATCH bpf-next v4 06/11] bpf: make reference tracking generic

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Date:   Mon, 21 Sep 2020 13:12:22 +0100
From:   Lorenz Bauer <lmb@...udflare.com>
To:     ast@...nel.org, daniel@...earbox.net
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        Lorenz Bauer <lmb@...udflare.com>,
        Andrii Nakryiko <andriin@...com>,
        Martin KaFai Lau <kafai@...com>
Subject: [PATCH bpf-next v4 06/11] bpf: make reference tracking generic

Instead of dealing with reg->ref_obj_id individually for every arg type that
needs it, rely on the fact that ref_obj_id is zero if the register is not
reference tracked.

Signed-off-by: Lorenz Bauer <lmb@...udflare.com>
Acked-by: Andrii Nakryiko <andriin@...com>
Acked-by: Martin KaFai Lau <kafai@...com>
---
 kernel/bpf/verifier.c | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 99c0d7adcb1e..0f7a9c65db5c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3983,15 +3983,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		/* Any sk pointer can be ARG_PTR_TO_SOCK_COMMON */
 		if (!type_is_sk_pointer(type))
 			goto err_type;
-		if (reg->ref_obj_id) {
-			if (meta->ref_obj_id) {
-				verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
-					regno, reg->ref_obj_id,
-					meta->ref_obj_id);
-				return -EFAULT;
-			}
-			meta->ref_obj_id = reg->ref_obj_id;
-		}
 	} else if (arg_type == ARG_PTR_TO_SOCKET ||
 		   arg_type == ARG_PTR_TO_SOCKET_OR_NULL) {
 		expected_type = PTR_TO_SOCKET;
@@ -4040,13 +4031,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			/* final test in check_stack_boundary() */;
 		else if (type != expected_type)
 			goto err_type;
-		if (meta->ref_obj_id) {
-			verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
-				regno, reg->ref_obj_id,
-				meta->ref_obj_id);
-			return -EFAULT;
-		}
-		meta->ref_obj_id = reg->ref_obj_id;
 	} else if (arg_type_is_int_ptr(arg_type)) {
 		expected_type = PTR_TO_STACK;
 		if (!type_is_pkt_pointer(type) &&
@@ -4078,6 +4062,16 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		}
 	}
 
+	if (reg->ref_obj_id) {
+		if (meta->ref_obj_id) {
+			verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
+				regno, reg->ref_obj_id,
+				meta->ref_obj_id);
+			return -EFAULT;
+		}
+		meta->ref_obj_id = reg->ref_obj_id;
+	}
+
 	if (arg_type == ARG_CONST_MAP_PTR) {
 		/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
 		meta->map_ptr = reg->map_ptr;
-- 
2.25.1