iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

selftests/bpf: add a test for iter/task_vma for short-lived processes

Browse Source 
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>
This commit is contained in:
Kui-Feng Lee 2022-12-16 14:18:55 -08:00 committed by Alexei Starovoitov
parent 7ff94f276f
commit b7793c8db7
1 changed files with 73 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

73
tools/testing/selftests/bpf/prog_tests/bpf_iter.c
View File

@ -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"))