selftests/bpf: add trusted global subprog arg tests

Add a bunch of test cases validating behavior of __arg_trusted and its
combination with __arg_nullable tag. We also validate CO-RE flavor
support by kernel for __arg_trusted args.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240130000648.2144827-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/prog_tests/verifier.c

@@ -28,6 +28,7 @@
 #include "verifier_div0.skel.h"
 #include "verifier_div_overflow.skel.h"
 #include "verifier_global_subprogs.skel.h"
+#include "verifier_global_ptr_args.skel.h"
 #include "verifier_gotol.skel.h"
 #include "verifier_helper_access_var_len.skel.h"
 #include "verifier_helper_packet_access.skel.h"
@@ -140,6 +141,7 @@ void test_verifier_direct_stack_access_wraparound(void) { RUN(verifier_direct_st
 void test_verifier_div0(void)                 { RUN(verifier_div0); }
 void test_verifier_div_overflow(void)         { RUN(verifier_div_overflow); }
 void test_verifier_global_subprogs(void)      { RUN(verifier_global_subprogs); }
+void test_verifier_global_ptr_args(void)      { RUN(verifier_global_ptr_args); }
 void test_verifier_gotol(void)                { RUN(verifier_gotol); }
 void test_verifier_helper_access_var_len(void) { RUN(verifier_helper_access_var_len); }
 void test_verifier_helper_packet_access(void) { RUN(verifier_helper_packet_access); }

tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c

@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+#include "bpf_misc.h"
+#include "xdp_metadata.h"
+#include "bpf_kfuncs.h"
+
+extern struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym __weak;
+extern void bpf_task_release(struct task_struct *p) __ksym __weak;
+
+__weak int subprog_trusted_task_nullable(struct task_struct *task __arg_trusted __arg_nullable)
+{
+	if (!task)
+		return 0;
+	return task->pid + task->tgid;
+}
+
+SEC("?kprobe")
+__success __log_level(2)
+__msg("Validating subprog_trusted_task_nullable() func#1...")
+__msg(": R1=trusted_ptr_or_null_task_struct(")
+int trusted_task_arg_nullable(void *ctx)
+{
+	struct task_struct *t = bpf_get_current_task_btf();
+
+	return subprog_trusted_task_nullable(t) + subprog_trusted_task_nullable(NULL);
+}
+
+__weak int subprog_trusted_task_nonnull(struct task_struct *task __arg_trusted)
+{
+	return task->pid + task->tgid;
+}
+
+SEC("?kprobe")
+__failure __log_level(2)
+__msg("R1 type=scalar expected=ptr_, trusted_ptr_, rcu_ptr_")
+__msg("Caller passes invalid args into func#1 ('subprog_trusted_task_nonnull')")
+int trusted_task_arg_nonnull_fail1(void *ctx)
+{
+	return subprog_trusted_task_nonnull(NULL);
+}
+
+SEC("?tp_btf/task_newtask")
+__failure __log_level(2)
+__msg("R1 type=ptr_or_null_ expected=ptr_, trusted_ptr_, rcu_ptr_")
+__msg("Caller passes invalid args into func#1 ('subprog_trusted_task_nonnull')")
+int trusted_task_arg_nonnull_fail2(void *ctx)
+{
+	struct task_struct *t = bpf_get_current_task_btf();
+	struct task_struct *nullable;
+	int res;
+
+	nullable = bpf_task_acquire(t);
+
+	 /* should fail, PTR_TO_BTF_ID_OR_NULL */
+	res = subprog_trusted_task_nonnull(nullable);
+
+	if (nullable)
+		bpf_task_release(nullable);
+
+	return res;
+}
+
+SEC("?kprobe")
+__success __log_level(2)
+__msg("Validating subprog_trusted_task_nonnull() func#1...")
+__msg(": R1=trusted_ptr_task_struct(")
+int trusted_task_arg_nonnull(void *ctx)
+{
+	struct task_struct *t = bpf_get_current_task_btf();
+
+	return subprog_trusted_task_nonnull(t);
+}
+
+struct task_struct___local {} __attribute__((preserve_access_index));
+
+__weak int subprog_nullable_task_flavor(
+	struct task_struct___local *task __arg_trusted __arg_nullable)
+{
+	char buf[16];
+
+	if (!task)
+		return 0;
+
+	return bpf_copy_from_user_task(&buf, sizeof(buf), NULL, (void *)task, 0);
+}
+
+SEC("?uprobe.s")
+__success __log_level(2)
+__msg("Validating subprog_nullable_task_flavor() func#1...")
+__msg(": R1=trusted_ptr_or_null_task_struct(")
+int flavor_ptr_nullable(void *ctx)
+{
+	struct task_struct___local *t = (void *)bpf_get_current_task_btf();
+
+	return subprog_nullable_task_flavor(t);
+}
+
+__weak int subprog_nonnull_task_flavor(struct task_struct___local *task __arg_trusted)
+{
+	char buf[16];
+
+	return bpf_copy_from_user_task(&buf, sizeof(buf), NULL, (void *)task, 0);
+}
+
+SEC("?uprobe.s")
+__success __log_level(2)
+__msg("Validating subprog_nonnull_task_flavor() func#1...")
+__msg(": R1=trusted_ptr_task_struct(")
+int flavor_ptr_nonnull(void *ctx)
+{
+	struct task_struct *t = bpf_get_current_task_btf();
+
+	return subprog_nonnull_task_flavor((void *)t);
+}
+
+__weak int subprog_trusted_destroy(struct task_struct *task __arg_trusted)
+{
+	bpf_task_release(task); /* should be rejected */
+
+	return 0;
+}
+
+SEC("?tp_btf/task_newtask")
+__failure __log_level(2)
+__msg("release kernel function bpf_task_release expects refcounted PTR_TO_BTF_ID")
+int BPF_PROG(trusted_destroy_fail, struct task_struct *task, u64 clone_flags)
+{
+	return subprog_trusted_destroy(task);
+}
+
+__weak int subprog_trusted_acq_rel(struct task_struct *task __arg_trusted)
+{
+	struct task_struct *owned;
+
+	owned = bpf_task_acquire(task);
+	if (!owned)
+		return 0;
+
+	bpf_task_release(owned); /* this one is OK, we acquired it locally */
+
+	return 0;
+}
+
+SEC("?tp_btf/task_newtask")
+__success __log_level(2)
+int BPF_PROG(trusted_acq_rel, struct task_struct *task, u64 clone_flags)
+{
+	return subprog_trusted_acq_rel(task);
+}
+
+char _license[] SEC("license") = "GPL";