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authorKui-Feng Lee <kuifeng@meta.com>2022-12-17 01:18:55 +0300
committerAlexei Starovoitov <ast@kernel.org>2022-12-29 01:11:48 +0300
commitb7793c8db7d9beb903bb42f52872b5b46abdcb88 (patch)
tree5647f0a167f6d19d803bba618e0ba12eac578691 /tools/testing
parent7ff94f276f8ea05df82eb115225e9b26f47a3347 (diff)
downloadlinux-b7793c8db7d9beb903bb42f52872b5b46abdcb88.tar.xz
selftests/bpf: add a test for iter/task_vma for short-lived processes
When a task iterator traverses vma(s), it is possible task->mm might become invalid in the middle of traversal and this may cause kernel misbehave (e.g., crash) This test case creates iterators repeatedly and forks short-lived processes in the background to detect this bug. The test will last for 3 seconds to get the chance to trigger the issue. Signed-off-by: Kui-Feng Lee <kuifeng@meta.com> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/r/20221216221855.4122288-3-kuifeng@meta.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'tools/testing')
-rw-r--r--tools/testing/selftests/bpf/prog_tests/bpf_iter.c73
1 files changed, 73 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index 6f8ed61fc4b4..3af6450763e9 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -1465,6 +1465,77 @@ out:
bpf_iter_task_vma__destroy(skel);
}
+static void test_task_vma_dead_task(void)
+{
+ struct bpf_iter_task_vma *skel;
+ int wstatus, child_pid = -1;
+ time_t start_tm, cur_tm;
+ int err, iter_fd = -1;
+ int wait_sec = 3;
+
+ skel = bpf_iter_task_vma__open();
+ if (!ASSERT_OK_PTR(skel, "bpf_iter_task_vma__open"))
+ return;
+
+ skel->bss->pid = getpid();
+
+ err = bpf_iter_task_vma__load(skel);
+ if (!ASSERT_OK(err, "bpf_iter_task_vma__load"))
+ goto out;
+
+ skel->links.proc_maps = bpf_program__attach_iter(
+ skel->progs.proc_maps, NULL);
+
+ if (!ASSERT_OK_PTR(skel->links.proc_maps, "bpf_program__attach_iter")) {
+ skel->links.proc_maps = NULL;
+ goto out;
+ }
+
+ start_tm = time(NULL);
+ cur_tm = start_tm;
+
+ child_pid = fork();
+ if (child_pid == 0) {
+ /* Fork short-lived processes in the background. */
+ while (cur_tm < start_tm + wait_sec) {
+ system("echo > /dev/null");
+ cur_tm = time(NULL);
+ }
+ exit(0);
+ }
+
+ if (!ASSERT_GE(child_pid, 0, "fork_child"))
+ goto out;
+
+ while (cur_tm < start_tm + wait_sec) {
+ iter_fd = bpf_iter_create(bpf_link__fd(skel->links.proc_maps));
+ if (!ASSERT_GE(iter_fd, 0, "create_iter"))
+ goto out;
+
+ /* Drain all data from iter_fd. */
+ while (cur_tm < start_tm + wait_sec) {
+ err = read_fd_into_buffer(iter_fd, task_vma_output, CMP_BUFFER_SIZE);
+ if (!ASSERT_GE(err, 0, "read_iter_fd"))
+ goto out;
+
+ cur_tm = time(NULL);
+
+ if (err == 0)
+ break;
+ }
+
+ close(iter_fd);
+ iter_fd = -1;
+ }
+
+ check_bpf_link_info(skel->progs.proc_maps);
+
+out:
+ waitpid(child_pid, &wstatus, 0);
+ close(iter_fd);
+ bpf_iter_task_vma__destroy(skel);
+}
+
void test_bpf_sockmap_map_iter_fd(void)
{
struct bpf_iter_sockmap *skel;
@@ -1586,6 +1657,8 @@ void test_bpf_iter(void)
test_task_file();
if (test__start_subtest("task_vma"))
test_task_vma();
+ if (test__start_subtest("task_vma_dead_task"))
+ test_task_vma_dead_task();
if (test__start_subtest("task_btf"))
test_task_btf();
if (test__start_subtest("tcp4"))