[RFC,bpf-next,6/6] selftests/bpf: Add test case for element reuse in htab map

Commit Message

Hou Tao Dec. 30, 2022, 4:11 a.m. UTC

From: Hou Tao <[e-mail]>

The immediate reuse of free htab elements can lead to two problems:
1) lookup may get unexpected map value if the found element is deleted
and then reused.
2) the reinitialization of spin-lock in map value after reuse may
corrupt lookup with BPF_F_LOCK flag and result in hard lock-up.

So add one test case to demonostrate these two problems.

Signed-off-by: Hou Tao <[e-mail]>
---
 .../selftests/bpf/prog_tests/htab_reuse.c     | 111 ++++++++++++++++++
 .../testing/selftests/bpf/progs/htab_reuse.c  |  19 +++
 2 files changed, 130 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/htab_reuse.c
 create mode 100644 tools/testing/selftests/bpf/progs/htab_reuse.c

Patch

diff --git a/tools/testing/selftests/bpf/prog_tests/htab_reuse.c b/tools/testing/selftests/bpf/prog_tests/htab_reuse.c
new file mode 100644
index 000000000000..995972958d1d
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/htab_reuse.c
@@ -0,0 +1,111 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2022. Huawei Technologies Co., Ltd */
+#define _GNU_SOURCE
+#include <sched.h>
+#include <stdbool.h>
+#include <test_progs.h>
+#include "htab_reuse.skel.h"
+
+struct htab_op_ctx {
+	int fd;
+	int loop;
+	bool stop;
+};
+
+struct htab_val {
+	unsigned int lock;
+	unsigned int data;
+};
+
+static void *htab_lookup_fn(void *arg)
+{
+	struct htab_op_ctx *ctx = arg;
+	int ret = 0, i = 0;
+
+        while (i++ < ctx->loop && !ctx->stop) {
+		struct htab_val value;
+		unsigned int key;
+		int err;
+
+		/*
+		 * Use BPF_F_LOCK to use spin-lock in map value. And also
+		 * check whether or not an unexpected value is returned.
+		 */
+		key = 7;
+                err = bpf_map_lookup_elem_flags(ctx->fd, &key, &value, BPF_F_LOCK);
+		if (!err && key != value.data)
+			ret = EINVAL;
+        }
+
+        return (void *)(long)ret;
+}
+
+static void *htab_update_fn(void *arg)
+{
+	struct htab_op_ctx *ctx = arg;
+	int i = 0;
+
+        while (i++ < ctx->loop && !ctx->stop) {
+		struct htab_val value;
+                unsigned int key;
+
+		key = 7;
+		value.lock = 0;
+		value.data = key;
+                bpf_map_update_elem(ctx->fd, &key, &value, BPF_F_LOCK);
+		bpf_map_delete_elem(ctx->fd, &key);
+
+		key = 24;
+		value.lock = 0;
+		value.data = key;
+                bpf_map_update_elem(ctx->fd, &key, &value, BPF_F_LOCK);
+		bpf_map_delete_elem(ctx->fd, &key);
+        }
+
+        return NULL;
+}
+
+void test_htab_reuse(void)
+{
+	unsigned int i, wr_nr = 1, rd_nr = 4;
+	pthread_t tids[wr_nr + rd_nr];
+	struct htab_reuse *skel;
+	struct htab_op_ctx ctx;
+	int err;
+
+	skel = htab_reuse__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "htab_reuse__open_and_load"))
+		return;
+
+	ctx.fd = bpf_map__fd(skel->maps.htab);
+	ctx.loop = 500;
+	ctx.stop = false;
+
+	memset(tids, 0, sizeof(tids));
+	for (i = 0; i < wr_nr; i++) {
+		err = pthread_create(&tids[i], NULL, htab_update_fn, &ctx);
+		if (!ASSERT_OK(err, "pthread_create")) {
+			ctx.stop = true;
+			goto reap;
+		}
+	}
+	for (i = 0; i < rd_nr; i++) {
+		err = pthread_create(&tids[i + wr_nr], NULL, htab_lookup_fn, &ctx);
+		if (!ASSERT_OK(err, "pthread_create")) {
+			ctx.stop = true;
+			goto reap;
+		}
+	}
+
+reap:
+	for (i = 0; i < wr_nr + rd_nr; i++) {
+		void *thread_err;
+
+		if (!tids[i])
+			continue;
+		thread_err = NULL;
+		pthread_join(tids[i], &thread_err);
+		ASSERT_NULL(thread_err, "thread error");
+	}
+	htab_reuse__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/htab_reuse.c b/tools/testing/selftests/bpf/progs/htab_reuse.c
new file mode 100644
index 000000000000..e6dcc70517f9
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/htab_reuse.c
@@ -0,0 +1,19 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2022. Huawei Technologies Co., Ltd */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct htab_val {
+	struct bpf_spin_lock lock;
+	unsigned int data;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 64);
+	__type(key, unsigned int);
+	__type(value, struct htab_val);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+} htab SEC(".maps");