[bpf-next,v2,2/2] selftests/bpf: Add tests for iter next method returning valid pointer

Commit Message

Juntong Deng Aug. 19, 2024, 10:19 a.m. UTC

This patch adds test cases for iter next method returning valid
pointer, which can also used as usage examples.

Currently iter next method should return valid pointer.

iter_next_trusted is the correct usage and test if iter next method
return valid pointer. bpf_iter_task_vma_next has KF_RET_NULL flag,
so the returned pointer may be NULL. We need to check if the pointer
is NULL before using it.

iter_next_trusted_or_null is the incorrect usage. There is no checking
before using the pointer, so it will be rejected by the verifier.

iter_next_rcu and iter_next_rcu_or_null are similar test cases for
KF_RCU_PROTECTED iterators.

iter_next_rcu_not_trusted is used to test that the pointer returned by
iter next method of KF_RCU_PROTECTED iterator cannot be passed in
KF_TRUSTED_ARGS kfuncs.

Signed-off-by: Juntong Deng <[e-mail]>
---
 .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  15 +++
 .../bpf/bpf_testmod/bpf_testmod_kfunc.h       |   4 +
 .../testing/selftests/bpf/prog_tests/iters.c  |   5 +-
 .../selftests/bpf/progs/iters_testmod.c       | 105 ++++++++++++++++++
 4 files changed, 128 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/bpf/progs/iters_testmod.c

Patch

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index a80b0d2c6f38..2cf0716ec64e 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -176,6 +176,18 @@  __bpf_kfunc void bpf_kfunc_dynptr_test(struct bpf_dynptr *ptr,
 {
 }
 
+__bpf_kfunc void bpf_kfunc_trusted_vma_test(struct vm_area_struct *ptr)
+{
+}
+
+__bpf_kfunc void bpf_kfunc_trusted_task_test(struct task_struct *ptr)
+{
+}
+
+__bpf_kfunc void bpf_kfunc_rcu_task_test(struct task_struct *ptr)
+{
+}
+
 __bpf_kfunc struct bpf_testmod_ctx *
 bpf_testmod_ctx_create(int *err)
 {
@@ -533,6 +545,9 @@  BTF_ID_FLAGS(func, bpf_iter_testmod_seq_next, KF_ITER_NEXT | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_iter_testmod_seq_destroy, KF_ITER_DESTROY)
 BTF_ID_FLAGS(func, bpf_kfunc_common_test)
 BTF_ID_FLAGS(func, bpf_kfunc_dynptr_test)
+BTF_ID_FLAGS(func, bpf_kfunc_trusted_vma_test, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_kfunc_trusted_task_test, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_kfunc_rcu_task_test, KF_RCU)
 BTF_ID_FLAGS(func, bpf_testmod_ctx_create, KF_ACQUIRE | KF_RET_NULL)
 BTF_ID_FLAGS(func, bpf_testmod_ctx_release, KF_RELEASE)
 BTF_KFUNCS_END(bpf_testmod_common_kfunc_ids)
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h
index e587a79f2239..db657f7a7802 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h
@@ -144,4 +144,8 @@  void bpf_kfunc_dynptr_test(struct bpf_dynptr *ptr, struct bpf_dynptr *ptr__nulla
 struct bpf_testmod_ctx *bpf_testmod_ctx_create(int *err) __ksym;
 void bpf_testmod_ctx_release(struct bpf_testmod_ctx *ctx) __ksym;
 
+void bpf_kfunc_trusted_vma_test(struct vm_area_struct *ptr) __ksym;
+void bpf_kfunc_trusted_task_test(struct task_struct *ptr) __ksym;
+void bpf_kfunc_rcu_task_test(struct task_struct *ptr) __ksym;
+
 #endif /* _BPF_TESTMOD_KFUNC_H */
diff --git a/tools/testing/selftests/bpf/prog_tests/iters.c b/tools/testing/selftests/bpf/prog_tests/iters.c
index 3c440370c1f0..89ff23c4a8bc 100644
--- a/tools/testing/selftests/bpf/prog_tests/iters.c
+++ b/tools/testing/selftests/bpf/prog_tests/iters.c
@@ -14,6 +14,7 @@ 
 #include "iters_state_safety.skel.h"
 #include "iters_looping.skel.h"
 #include "iters_num.skel.h"
+#include "iters_testmod.skel.h"
 #include "iters_testmod_seq.skel.h"
 #include "iters_task_vma.skel.h"
 #include "iters_task.skel.h"
@@ -297,8 +298,10 @@  void test_iters(void)
 	RUN_TESTS(iters);
 	RUN_TESTS(iters_css_task);
 
-	if (env.has_testmod)
+	if (env.has_testmod) {
+		RUN_TESTS(iters_testmod);
 		RUN_TESTS(iters_testmod_seq);
+	}
 
 	if (test__start_subtest("num"))
 		subtest_num_iters();
diff --git a/tools/testing/selftests/bpf/progs/iters_testmod.c b/tools/testing/selftests/bpf/progs/iters_testmod.c
new file mode 100644
index 000000000000..570dfadd4648
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/iters_testmod.c
@@ -0,0 +1,105 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include "bpf_experimental.h"
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+#include "../bpf_testmod/bpf_testmod_kfunc.h"
+
+char _license[] SEC("license") = "GPL";
+
+SEC("raw_tp/sys_enter")
+__success
+int iter_next_trusted(const void *ctx)
+{
+	struct task_struct *cur_task = bpf_get_current_task_btf();
+	struct bpf_iter_task_vma vma_it;
+	struct vm_area_struct *vma_ptr;
+
+	bpf_iter_task_vma_new(&vma_it, cur_task, 0);
+
+	vma_ptr = bpf_iter_task_vma_next(&vma_it);
+	if (vma_ptr == NULL)
+		goto out;
+
+	bpf_kfunc_trusted_vma_test(vma_ptr);
+out:
+	bpf_iter_task_vma_destroy(&vma_it);
+	return 0;
+}
+
+SEC("raw_tp/sys_enter")
+__failure __msg("Possibly NULL pointer passed to trusted arg0")
+int iter_next_trusted_or_null(const void *ctx)
+{
+	struct task_struct *cur_task = bpf_get_current_task_btf();
+	struct bpf_iter_task_vma vma_it;
+	struct vm_area_struct *vma_ptr;
+
+	bpf_iter_task_vma_new(&vma_it, cur_task, 0);
+
+	vma_ptr = bpf_iter_task_vma_next(&vma_it);
+
+	bpf_kfunc_trusted_vma_test(vma_ptr);
+
+	bpf_iter_task_vma_destroy(&vma_it);
+	return 0;
+}
+
+SEC("raw_tp/sys_enter")
+__success
+int iter_next_rcu(const void *ctx)
+{
+	struct task_struct *cur_task = bpf_get_current_task_btf();
+	struct bpf_iter_task task_it;
+	struct task_struct *task_ptr;
+
+	bpf_iter_task_new(&task_it, cur_task, 0);
+
+	task_ptr = bpf_iter_task_next(&task_it);
+	if (task_ptr == NULL)
+		goto out;
+
+	bpf_kfunc_rcu_task_test(task_ptr);
+out:
+	bpf_iter_task_destroy(&task_it);
+	return 0;
+}
+
+SEC("raw_tp/sys_enter")
+__failure __msg("Possibly NULL pointer passed to trusted arg0")
+int iter_next_rcu_or_null(const void *ctx)
+{
+	struct task_struct *cur_task = bpf_get_current_task_btf();
+	struct bpf_iter_task task_it;
+	struct task_struct *task_ptr;
+
+	bpf_iter_task_new(&task_it, cur_task, 0);
+
+	task_ptr = bpf_iter_task_next(&task_it);
+
+	bpf_kfunc_rcu_task_test(task_ptr);
+
+	bpf_iter_task_destroy(&task_it);
+	return 0;
+}
+
+SEC("raw_tp/sys_enter")
+__failure __msg("R1 must be referenced or trusted")
+int iter_next_rcu_not_trusted(const void *ctx)
+{
+	struct task_struct *cur_task = bpf_get_current_task_btf();
+	struct bpf_iter_task task_it;
+	struct task_struct *task_ptr;
+
+	bpf_iter_task_new(&task_it, cur_task, 0);
+
+	task_ptr = bpf_iter_task_next(&task_it);
+	if (task_ptr == NULL)
+		goto out;
+
+	bpf_kfunc_trusted_task_test(task_ptr);
+out:
+	bpf_iter_task_destroy(&task_it);
+	return 0;
+}