[PATCH bpf-next v1 09/12] bpf: Check global subprog BTF-ID arguments in the common path

[Amery Hung <ameryhung@gmail.com>]

Route global ARG_PTR_TO_BTF_ID arguments through check_func_arg(). Use
vmlinux BTF for their type match and retain the global-subprogram rules
instead of applying kfunc-only trusted-pointer validation or runtime type
resolution.

The common nullability check now rejects non-nullable global BTF-ID
arguments before register-type matching. Update the corresponding
verifier log expectations.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
 kernel/bpf/verifier.c                         | 31 +++++--------------
 .../bpf/progs/verifier_global_ptr_args.c      |  4 +--
 2 files changed, 10 insertions(+), 25 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 4a5c682ee73c..73a1c4877427 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9512,7 +9512,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, u32 slot, u32 p
 	case ARG_PTR_TO_BTF_ID_SOCK_COMMON:
 	{
 		const u32 *arg_btf_id = fn->arg_btf_id[arg];
-		const struct btf *arg_btf = meta->btf ?: btf_vmlinux;
+		const struct btf *arg_btf = is_kfunc(meta) ? meta->btf : btf_vmlinux;
 
 		if (!meta->btf) {
 			const struct bpf_reg_types *compatible;
@@ -9540,8 +9540,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, u32 slot, u32 p
 			}
 		}
 
-		if (meta->btf && (!is_trusted_reg(env, reg) ||
-				  bpf_type_has_unsafe_modifiers(reg->type))) {
+		if (is_kfunc(meta) && (!is_trusted_reg(env, reg) ||
+				       bpf_type_has_unsafe_modifiers(reg->type))) {
 			if (!(arg_type & MEM_RCU)) {
 				const char *actual_type, *arg_name, *expected_type;
 
@@ -10817,6 +10817,8 @@ static void gen_subprog_arg_proto(const struct bpf_subprog_info *sub, const stru
 			arg_type = ARG_IGNORE;
 		} else if (base_type(arg_type) == ARG_PTR_TO_ARENA) {
 			arg_type |= PTR_MAYBE_NULL;
+		} else if (base_type(arg_type) == ARG_PTR_TO_BTF_ID) {
+			proto->arg_btf_id[arg] = &sub->args[slot].btf_id;
 		}
 		proto->arg_type[arg] = arg_type;
 		t = btf_type_skip_modifiers(btf, args[arg].type, NULL);
@@ -10883,7 +10885,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 
 		if (arg_type == ARG_SCALAR || arg_type == ARG_IGNORE ||
 		    arg_type == ARG_PTR_TO_CTX || arg_type == ARG_PTR_TO_DYNPTR ||
-		    base_type(arg_type) == ARG_PTR_TO_ARENA) {
+		    base_type(arg_type) == ARG_PTR_TO_ARENA ||
+		    base_type(arg_type) == ARG_PTR_TO_BTF_ID) {
 			ret = check_func_arg(env, arg, slot, 0, &meta, env->insn_idx);
 			if (ret)
 				return ret;
@@ -10911,24 +10914,6 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 					reg_arg_name(env, argno));
 				return -EINVAL;
 			}
-		} else if (base_type(arg_type) == ARG_PTR_TO_BTF_ID) {
-			int err;
-
-			if (bpf_register_is_null(reg) && type_may_be_null(arg_type)) {
-				err = mark_arg_precision(env, argno);
-				if (err)
-					return err;
-				continue;
-			}
-
-			err = check_reg_type(env, reg, argno, arg_type, &meta);
-			err = err ?: check_func_arg_reg_off(env, reg, argno, arg_type);
-			if (!err && base_type(reg->type) == PTR_TO_BTF_ID)
-				err = process_arg_ptr_to_btf_id(env, reg, argno, arg_type,
-								btf_vmlinux, sub->args[slot].btf_id,
-								&meta, env->insn_idx);
-			if (err)
-				return err;
 		} else {
 			verifier_bug(env, "unrecognized %s type %d",
 				     reg_arg_name(env, argno), arg_type);
@@ -13073,7 +13058,7 @@ static int resolve_func_arg_type(struct bpf_verifier_env *env,
 	if (base_type(*arg_type) != ARG_PTR_TO_BTF_ID)
 		return 0;
 
-	if (!meta->btf || arg_type_is_release(*arg_type) ||
+	if (!is_kfunc(meta) || arg_type_is_release(*arg_type) ||
 	    base_type(reg->type) == PTR_TO_BTF_ID ||
 	    reg2btf_ids[base_type(reg->type)])
 		return 0;
diff --git a/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c b/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c
index 10019af5eb74..f639e2767e35 100644
--- a/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c
+++ b/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c
@@ -87,7 +87,7 @@ __weak int subprog_trusted_task_nonnull(struct task_struct *task __arg_trusted)
 
 SEC("?kprobe")
 __failure __log_level(2)
-__msg("R1 type=scalar expected=ptr_, trusted_ptr_, rcu_ptr_")
+__msg("Possibly NULL pointer passed to trusted R1")
 __msg("Caller passes invalid args into func#1 ('subprog_trusted_task_nonnull')")
 int trusted_task_arg_nonnull_fail1(void *ctx)
 {
@@ -96,7 +96,7 @@ int trusted_task_arg_nonnull_fail1(void *ctx)
 
 SEC("?tp_btf/task_newtask")
 __failure __log_level(2)
-__msg("R1 type=trusted_ptr_or_null_ expected=ptr_, trusted_ptr_, rcu_ptr_")
+__msg("Possibly NULL pointer passed to trusted R1")
 __msg("Caller passes invalid args into func#1 ('subprog_trusted_task_nonnull')")
 int trusted_task_arg_nonnull_fail2(void *ctx)
 {
-- 
2.52.0