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From: David Vernet <void@manifault.com>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
	martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
	john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
	haoluo@google.com, jolsa@kernel.org,
	linux-kernel@vger.kernel.org, kernel-team@meta.com
Subject: [PATCH bpf-next v2 3/5] bpf/selftests: Test using global cpumask kptr with RCU
Date: Thu, 16 Mar 2023 00:40:26 -0500	[thread overview]
Message-ID: <20230316054028.88924-4-void@manifault.com> (raw)
In-Reply-To: <20230316054028.88924-1-void@manifault.com>

Now that struct bpf_cpumask * is considered an RCU-safe type according
to the verifier, we should add tests that validate its common usages.
This patch adds those tests to the cpumask test suite. A subsequent
changes will remove bpf_cpumask_kptr_get(), and will adjust the selftest
and BPF documentation accordingly.

Signed-off-by: David Vernet <void@manifault.com>
---
 .../selftests/bpf/prog_tests/cpumask.c        |  1 +
 .../selftests/bpf/progs/cpumask_common.h      |  6 ++
 .../selftests/bpf/progs/cpumask_failure.c     | 62 +++++++++++++++++++
 .../selftests/bpf/progs/cpumask_success.c     | 33 ++++++++++
 4 files changed, 102 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/cpumask.c b/tools/testing/selftests/bpf/prog_tests/cpumask.c
index 5fbe457c4ebe..6c0fe23498c7 100644
--- a/tools/testing/selftests/bpf/prog_tests/cpumask.c
+++ b/tools/testing/selftests/bpf/prog_tests/cpumask.c
@@ -17,6 +17,7 @@ static const char * const cpumask_success_testcases[] = {
 	"test_insert_leave",
 	"test_insert_remove_release",
 	"test_insert_kptr_get_release",
+	"test_global_mask_rcu",
 };
 
 static void verify_success(const char *prog_name)
diff --git a/tools/testing/selftests/bpf/progs/cpumask_common.h b/tools/testing/selftests/bpf/progs/cpumask_common.h
index 65e5496ca1b2..7623782fbd62 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_common.h
+++ b/tools/testing/selftests/bpf/progs/cpumask_common.h
@@ -9,6 +9,9 @@
 
 int err;
 
+#define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8)))
+private(MASK) static struct bpf_cpumask __kptr * global_mask;
+
 struct __cpumask_map_value {
 	struct bpf_cpumask __kptr * cpumask;
 };
@@ -51,6 +54,9 @@ void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask *src) __ksym
 u32 bpf_cpumask_any(const struct cpumask *src) __ksym;
 u32 bpf_cpumask_any_and(const struct cpumask *src1, const struct cpumask *src2) __ksym;
 
+void bpf_rcu_read_lock(void) __ksym;
+void bpf_rcu_read_unlock(void) __ksym;
+
 static inline const struct cpumask *cast(struct bpf_cpumask *cpumask)
 {
 	return (const struct cpumask *)cpumask;
diff --git a/tools/testing/selftests/bpf/progs/cpumask_failure.c b/tools/testing/selftests/bpf/progs/cpumask_failure.c
index cfe83f0ef9e2..9f726d55f747 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_failure.c
+++ b/tools/testing/selftests/bpf/progs/cpumask_failure.c
@@ -127,3 +127,65 @@ int BPF_PROG(test_cpumask_null, struct task_struct *task, u64 clone_flags)
 
 	return 0;
 }
+
+SEC("tp_btf/task_newtask")
+__failure __msg("R2 must be a rcu pointer")
+int BPF_PROG(test_global_mask_out_of_rcu, struct task_struct *task, u64 clone_flags)
+{
+	struct bpf_cpumask *local, *prev;
+
+	local = create_cpumask();
+	if (!local)
+		return 0;
+
+	prev = bpf_kptr_xchg(&global_mask, local);
+	if (prev) {
+		bpf_cpumask_release(prev);
+		err = 3;
+		return 0;
+	}
+
+	bpf_rcu_read_lock();
+	local = global_mask;
+	if (!local) {
+		err = 4;
+		bpf_rcu_read_unlock();
+		return 0;
+	}
+
+	bpf_rcu_read_unlock();
+
+	/* RCU region is exited before calling KF_RCU kfunc. */
+
+	bpf_cpumask_test_cpu(0, (const struct cpumask *)local);
+
+	return 0;
+}
+
+SEC("tp_btf/task_newtask")
+__failure __msg("NULL pointer passed to trusted arg1")
+int BPF_PROG(test_global_mask_no_null_check, struct task_struct *task, u64 clone_flags)
+{
+	struct bpf_cpumask *local, *prev;
+
+	local = create_cpumask();
+	if (!local)
+		return 0;
+
+	prev = bpf_kptr_xchg(&global_mask, local);
+	if (prev) {
+		bpf_cpumask_release(prev);
+		err = 3;
+		return 0;
+	}
+
+	bpf_rcu_read_lock();
+	local = global_mask;
+
+	/* No NULL check is performed on global cpumask kptr. */
+	bpf_cpumask_test_cpu(0, (const struct cpumask *)local);
+
+	bpf_rcu_read_unlock();
+
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/cpumask_success.c b/tools/testing/selftests/bpf/progs/cpumask_success.c
index 97ed08c4ff03..fe928ff72a06 100644
--- a/tools/testing/selftests/bpf/progs/cpumask_success.c
+++ b/tools/testing/selftests/bpf/progs/cpumask_success.c
@@ -423,3 +423,36 @@ int BPF_PROG(test_insert_kptr_get_release, struct task_struct *task, u64 clone_f
 
 	return 0;
 }
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(test_global_mask_rcu, struct task_struct *task, u64 clone_flags)
+{
+	struct bpf_cpumask *local, *prev;
+
+	if (!is_test_task())
+		return 0;
+
+	local = create_cpumask();
+	if (!local)
+		return 0;
+
+	prev = bpf_kptr_xchg(&global_mask, local);
+	if (prev) {
+		bpf_cpumask_release(prev);
+		err = 3;
+		return 0;
+	}
+
+	bpf_rcu_read_lock();
+	local = global_mask;
+	if (!local) {
+		err = 4;
+		bpf_rcu_read_unlock();
+		return 0;
+	}
+
+	bpf_cpumask_test_cpu(0, (const struct cpumask *)local);
+	bpf_rcu_read_unlock();
+
+	return 0;
+}
-- 
2.39.0


  parent reply	other threads:[~2023-03-16  5:40 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-16  5:40 [PATCH bpf-next v2 0/5] Make struct bpf_cpumask RCU safe David Vernet
2023-03-16  5:40 ` [PATCH bpf-next v2 1/5] bpf: Free struct bpf_cpumask in call_rcu handler David Vernet
2023-03-16  5:40 ` [PATCH bpf-next v2 2/5] bpf: Mark struct bpf_cpumask as rcu protected David Vernet
2023-03-16  5:40 ` David Vernet [this message]
2023-03-16  5:40 ` [PATCH bpf-next v2 4/5] bpf: Remove bpf_cpumask_kptr_get() kfunc David Vernet
2023-03-16  5:40 ` [PATCH bpf-next v2 5/5] bpf,docs: Remove bpf_cpumask_kptr_get() from documentation David Vernet
2023-03-16 19:40 ` [PATCH bpf-next v2 0/5] Make struct bpf_cpumask RCU safe patchwork-bot+netdevbpf

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