From: Hou Tao <houtao1@xxxxxxxxxx>
Test race between the release of map ref and bpf_timer_init():
1) create one thread to add array map with bpf_timer into array of
arrays map repeatedly.
2) create another thread to call getpgid() and call bpf_timer_init()
in the attached bpf program repeatedly.
3) synchronize these two threads through pthread barrier.
It is a bit hard to trigger the kmemleak by only running the test. I
managed to reproduce the kmemleak by injecting a delay between
t->timer.function = bpf_timer_cb and timer->timer = t in
bpf_timer_init().
The following is the output of kmemleak after reproducing:
unreferenced object 0xffff8881163d3780 (size 96):
comm "test_progs", pid 539, jiffies 4295358164 (age 23.276s)
hex dump (first 32 bytes):
80 37 3d 16 81 88 ff ff 00 00 00 00 00 00 00 00 .7=.............
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<00000000bbc3f059>] __kmem_cache_alloc_node+0x3b1/0x4a0
[<00000000a24ddf4d>] __kmalloc_node+0x57/0x140
[<000000004d577dbf>] bpf_map_kmalloc_node+0x5f/0x180
[<00000000bd8428d3>] bpf_timer_init+0xf6/0x1b0
[<0000000086d87323>] 0xffffffffc000c94e
[<000000005a09e655>] trace_call_bpf+0xc5/0x1c0
[<0000000051ab837b>] kprobe_perf_func+0x51/0x260
[<000000000069bbd1>] kprobe_dispatcher+0x61/0x70
[<000000007dceb75b>] kprobe_ftrace_handler+0x168/0x240
[<00000000d8721bd7>] 0xffffffffc02010f7
[<00000000e885b809>] __x64_sys_getpgid+0x1/0x20
[<000000007be835d8>] entry_SYSCALL_64_after_hwframe+0x6e/0xd8
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
.../bpf/prog_tests/timer_init_race.c | 138 ++++++++++++++++++
.../selftests/bpf/progs/timer_init_race.c | 56 +++++++
2 files changed, 194 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/timer_init_race.c
create mode 100644 tools/testing/selftests/bpf/progs/timer_init_race.c
diff --git a/tools/testing/selftests/bpf/prog_tests/timer_init_race.c b/tools/testing/selftests/bpf/prog_tests/timer_init_race.c
new file mode 100644
index 000000000000..7bd57459e504
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/timer_init_race.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2023. Huawei Technologies Co., Ltd */
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include "timer_init_race.skel.h"
+
+struct thread_ctx {
+ struct bpf_map_create_opts opts;
+ pthread_barrier_t barrier;
+ int outer_map_fd;
+ int start, abort;
+ int loop, err;
+};
+
+static int wait_for_start_or_abort(struct thread_ctx *ctx)
+{
+ while (!ctx->start && !ctx->abort)
+ usleep(1);
+ return ctx->abort ? -1 : 0;
+}
+
+static void *close_map_fn(void *data)
+{
+ struct thread_ctx *ctx = data;
+ int loop = ctx->loop, err = 0;
+
+ if (wait_for_start_or_abort(ctx) < 0)
+ return NULL;
+
+ while (loop-- > 0) {
+ int fd, zero = 0, i;
+ volatile int s = 0;
+
+ fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, 4, sizeof(struct bpf_timer),
+ 1, &ctx->opts);
+ if (fd < 0) {
+ err |= 1;
+ pthread_barrier_wait(&ctx->barrier);
+ continue;
+ }
+
+ if (bpf_map_update_elem(ctx->outer_map_fd, &zero, &fd, 0) < 0)
+ err |= 2;
+
+ pthread_barrier_wait(&ctx->barrier);
+ /* let bpf_timer_init run first */
+ for (i = 0; i < 5000; i++)
+ s++;
+ close(fd);
+ }
+
+ ctx->err = err;
+
+ return NULL;
+}
+
+static void *init_timer_fn(void *data)
+{
+ struct thread_ctx *ctx = data;
+ int loop = ctx->loop;
+
+ if (wait_for_start_or_abort(ctx) < 0)
+ return NULL;
+
+ while (loop-- > 0) {
+ pthread_barrier_wait(&ctx->barrier);
+ syscall(SYS_getpgid);
+ }
+
+ return NULL;
+}
+
+void test_timer_init_race(void)
+{
+ struct timer_init_race *skel;
+ struct thread_ctx ctx;
+ pthread_t tid[2];
+ struct btf *btf;
+ int err;
+
+ skel = timer_init_race__open();
+ if (!ASSERT_OK_PTR(skel, "timer_init_race open"))
+ return;
+
+ err = timer_init_race__load(skel);
+ if (!ASSERT_EQ(err, 0, "timer_init_race load"))
+ goto out;
+
+ memset(&ctx, 0, sizeof(ctx));
+
+ btf = bpf_object__btf(skel->obj);
+ if (!ASSERT_OK_PTR(btf, "timer_init_race btf"))
+ goto out;
+
+ LIBBPF_OPTS_RESET(ctx.opts);
+ ctx.opts.btf_fd = bpf_object__btf_fd(skel->obj);
+ if (!ASSERT_GE((int)ctx.opts.btf_fd, 0, "btf_fd"))
+ goto out;
+ ctx.opts.btf_key_type_id = btf__find_by_name(btf, "int");
+ if (!ASSERT_GT(ctx.opts.btf_key_type_id, 0, "key_type_id"))
+ goto out;
+ ctx.opts.btf_value_type_id = btf__find_by_name_kind(btf, "inner_value", BTF_KIND_STRUCT);
+ if (!ASSERT_GT(ctx.opts.btf_value_type_id, 0, "value_type_id"))
+ goto out;
+
+ err = timer_init_race__attach(skel);
+ if (!ASSERT_EQ(err, 0, "timer_init_race attach"))
+ goto out;
+
+ skel->bss->tgid = getpid();
+
+ pthread_barrier_init(&ctx.barrier, NULL, 2);
+ ctx.outer_map_fd = bpf_map__fd(skel->maps.outer_map);
+ ctx.loop = 8;
+
+ err = pthread_create(&tid[0], NULL, close_map_fn, &ctx);
+ if (!ASSERT_OK(err, "close_thread"))
+ goto out;
+
+ err = pthread_create(&tid[1], NULL, init_timer_fn, &ctx);
+ if (!ASSERT_OK(err, "init_thread")) {
+ ctx.abort = 1;
+ pthread_join(tid[0], NULL);
+ goto out;
+ }
+
+ ctx.start = 1;
+ pthread_join(tid[0], NULL);
+ pthread_join(tid[1], NULL);
+
+ ASSERT_EQ(ctx.err, 0, "error");
+ ASSERT_EQ(skel->bss->cnt, 8, "cnt");
+out:
+ timer_init_race__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/timer_init_race.c b/tools/testing/selftests/bpf/progs/timer_init_race.c
new file mode 100644
index 000000000000..ba67cb178639
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/timer_init_race.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2023. Huawei Technologies Co., Ltd */
+#include <linux/bpf.h>
+#include <time.h>
+#include <bpf/bpf_helpers.h>
+
+#include "bpf_misc.h"
+
+struct inner_value {
+ struct bpf_timer timer;
+};
+
+struct inner_map_type {
+ __uint(type, BPF_MAP_TYPE_ARRAY);
+ __type(key, int);
+ __type(value, struct inner_value);
+ __uint(max_entries, 1);
+} inner_map SEC(".maps");
+
+struct {
+ __uint(type, BPF_MAP_TYPE_ARRAY_OF_MAPS);
+ __type(key, int);
+ __type(value, int);
+ __uint(max_entries, 1);
+ __array(values, struct inner_map_type);
+} outer_map SEC(".maps") = {
+ .values = {
+ [0] = &inner_map,
+ },
+};
+
+char _license[] SEC("license") = "GPL";
+
+int tgid = 0, cnt = 0;
+
+SEC("kprobe/" SYS_PREFIX "sys_getpgid")
+int do_timer_init(void *ctx)
+{
+ struct inner_map_type *map;
+ struct inner_value *value;
+ int zero = 0;
+
+ if ((bpf_get_current_pid_tgid() >> 32) != tgid)
+ return 0;
+
+ map = bpf_map_lookup_elem(&outer_map, &zero);
+ if (!map)
+ return 0;
+ value = bpf_map_lookup_elem(map, &zero);
+ if (!value)
+ return 0;
+ bpf_timer_init(&value->timer, map, CLOCK_MONOTONIC);
+ cnt++;
+
+ return 0;
+}
--
2.29.2
