selftests/bpf: Test deadlock from recursive bpf_task_storage_[get|delete]

Add a test with recursive bpf_task_storage_[get|delete] from fentry
programs on bpf_local_storage_lookup and bpf_local_storage_update. Without
proper deadlock prevent mechanism, this test would cause deadlock.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210225234319.336131-5-songliubraving@fb.com

diff --git a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
index dbb7525cdd5676fa8ee5e9bbc7965f7c2fb545d8..035c263aab1b12fe3a63fa65765600be595498eb 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
@@ -8,6 +8,7 @@
 #include <test_progs.h>
 #include "task_local_storage.skel.h"
 #include "task_local_storage_exit_creds.skel.h"
+#include "task_ls_recursion.skel.h"
 
 static void test_sys_enter_exit(void)
 {
@@ -60,10 +61,32 @@ out:
        task_local_storage_exit_creds__destroy(skel);
 }
 
+static void test_recursion(void)
+{
+       struct task_ls_recursion *skel;
+       int err;
+
+       skel = task_ls_recursion__open_and_load();
+       if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+               return;
+
+       err = task_ls_recursion__attach(skel);
+       if (!ASSERT_OK(err, "skel_attach"))
+               goto out;
+
+       /* trigger sys_enter, make sure it does not cause deadlock */
+       syscall(SYS_gettid);
+
+out:
+       task_ls_recursion__destroy(skel);
+}
+
 void test_task_local_storage(void)
 {
        if (test__start_subtest("sys_enter_exit"))
                test_sys_enter_exit();
        if (test__start_subtest("exit_creds"))
                test_exit_creds();
+       if (test__start_subtest("recursion"))
+               test_recursion();
 }

diff --git a/tools/testing/selftests/bpf/progs/task_ls_recursion.c b/tools/testing/selftests/bpf/progs/task_ls_recursion.c
new file mode 100644 (file)
index 0000000..564583d
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/task_ls_recursion.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+       __uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+       __uint(map_flags, BPF_F_NO_PREALLOC);
+       __type(key, int);
+       __type(value, long);
+} map_a SEC(".maps");
+
+struct {
+       __uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+       __uint(map_flags, BPF_F_NO_PREALLOC);
+       __type(key, int);
+       __type(value, long);
+} map_b SEC(".maps");
+
+SEC("fentry/bpf_local_storage_lookup")
+int BPF_PROG(on_lookup)
+{
+       struct task_struct *task = bpf_get_current_task_btf();
+
+       bpf_task_storage_delete(&map_a, task);
+       bpf_task_storage_delete(&map_b, task);
+       return 0;
+}
+
+SEC("fentry/bpf_local_storage_update")
+int BPF_PROG(on_update)
+{
+       struct task_struct *task = bpf_get_current_task_btf();
+       long *ptr;
+
+       ptr = bpf_task_storage_get(&map_a, task, 0,
+                                  BPF_LOCAL_STORAGE_GET_F_CREATE);
+       if (ptr)
+               *ptr += 1;
+
+       ptr = bpf_task_storage_get(&map_b, task, 0,
+                                  BPF_LOCAL_STORAGE_GET_F_CREATE);
+       if (ptr)
+               *ptr += 1;
+
+       return 0;
+}
+
+SEC("tp_btf/sys_enter")
+int BPF_PROG(on_enter, struct pt_regs *regs, long id)
+{
+       struct task_struct *task;
+       long *ptr;
+
+       task = bpf_get_current_task_btf();
+       ptr = bpf_task_storage_get(&map_a, task, 0,
+                                  BPF_LOCAL_STORAGE_GET_F_CREATE);
+       if (ptr)
+               *ptr = 200;
+
+       ptr = bpf_task_storage_get(&map_b, task, 0,
+                                  BPF_LOCAL_STORAGE_GET_F_CREATE);
+       if (ptr)
+               *ptr = 100;
+       return 0;
+}