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@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-7-lmb@cloudflare.com

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a0e9192..a4549b2 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4030,15 +4030,6 @@ 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;
@@ -4087,13 +4078,6 @@ 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) &&
@@ -4125,6 +4109,16 @@ 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;