[PATCH bpf-next 4/4] selftest/bpf: Test inode local storage recursion prevention
Song Liu
song at kernel.org
Tue Nov 12 08:26:00 UTC 2024
Add selftest for recursion prevention logic of bpf local storage.
When inode local storage function is traced, helpers that access inode
local storage should return -EBUSY.
The recurring program is attached to inode_storage_lookup(). This is not
an ideal target for recursion tests. However, given that the target
function have to take "struct inode *" argument, there isn't a better
target function for the tests.
Test results showed that inode_storage_lookup() is inlined in s390x.
Work around this by adding this test to DENYLIST.s390x.
Signed-off-by: Song Liu <song at kernel.org>
---
tools/testing/selftests/bpf/DENYLIST.s390x | 1 +
.../bpf/prog_tests/inode_local_storage.c | 72 +++++++++++++++
.../bpf/progs/inode_storage_recursion.c | 90 +++++++++++++++++++
3 files changed, 163 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/inode_local_storage.c
create mode 100644 tools/testing/selftests/bpf/progs/inode_storage_recursion.c
diff --git a/tools/testing/selftests/bpf/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index 3ebd77206f98..6b8c9c9ec754 100644
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -1,5 +1,6 @@
# TEMPORARY
# Alphabetical order
get_stack_raw_tp # user_stack corrupted user stack (no backchain userspace)
+inode_localstorage/recursion # target function (inode_storage_lookup) is inlined on s390)
stacktrace_build_id # compare_map_keys stackid_hmap vs. stackmap err -2 errno 2 (?)
verifier_iterating_callbacks
diff --git a/tools/testing/selftests/bpf/prog_tests/inode_local_storage.c b/tools/testing/selftests/bpf/prog_tests/inode_local_storage.c
new file mode 100644
index 000000000000..a9d9f77216f4
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/inode_local_storage.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+
+#include <stdio.h>
+#include <sys/stat.h>
+#include <test_progs.h>
+#include "inode_storage_recursion.skel.h"
+
+#define TDIR "/tmp/inode_local_storage"
+#define TDIR_PARENT "/tmp"
+
+static void test_recursion(void)
+{
+ struct inode_storage_recursion *skel;
+ struct bpf_prog_info info;
+ __u32 info_len = sizeof(info);
+ int err, prog_fd, map_fd, inode_fd = -1;
+ long value;
+
+ skel = inode_storage_recursion__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
+ return;
+
+ skel->bss->test_pid = getpid();
+
+ err = inode_storage_recursion__attach(skel);
+ if (!ASSERT_OK(err, "skel_attach"))
+ goto out;
+
+ err = mkdir(TDIR, 0755);
+ if (!ASSERT_OK(err, "mkdir " TDIR))
+ goto out;
+
+ inode_fd = open(TDIR_PARENT, O_RDONLY | O_CLOEXEC);
+ if (!ASSERT_OK_FD(inode_fd, "open inode_fd"))
+ goto out;
+
+ /* Detach so that the following lookup won't trigger
+ * trace_inode_storage_lookup and further change the values.
+ */
+ inode_storage_recursion__detach(skel);
+ map_fd = bpf_map__fd(skel->maps.inode_map);
+ err = bpf_map_lookup_elem(map_fd, &inode_fd, &value);
+ ASSERT_OK(err, "lookup inode_map");
+
+ /* Check trace_inode_mkdir for the reason that value == 201 */
+ ASSERT_EQ(value, 201, "inode_map value");
+ ASSERT_EQ(skel->bss->nr_del_errs, 1, "bpf_task_storage_delete busy");
+
+ prog_fd = bpf_program__fd(skel->progs.trace_inode_mkdir);
+ memset(&info, 0, sizeof(info));
+ err = bpf_prog_get_info_by_fd(prog_fd, &info, &info_len);
+ ASSERT_OK(err, "get prog info");
+ ASSERT_EQ(info.recursion_misses, 0, "trace_inode_mkdir prog recursion");
+
+ prog_fd = bpf_program__fd(skel->progs.trace_inode_storage_lookup);
+ memset(&info, 0, sizeof(info));
+ err = bpf_prog_get_info_by_fd(prog_fd, &info, &info_len);
+ ASSERT_OK(err, "get prog info");
+ ASSERT_EQ(info.recursion_misses, 3, "trace_inode_storage_lookup prog recursion");
+
+out:
+ rmdir(TDIR);
+ close(inode_fd);
+ inode_storage_recursion__destroy(skel);
+}
+
+void test_inode_localstorage(void)
+{
+ if (test__start_subtest("recursion"))
+ test_recursion();
+}
diff --git a/tools/testing/selftests/bpf/progs/inode_storage_recursion.c b/tools/testing/selftests/bpf/progs/inode_storage_recursion.c
new file mode 100644
index 000000000000..0ad36f8c6e04
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/inode_storage_recursion.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#ifndef EBUSY
+#define EBUSY 16
+#endif
+
+char _license[] SEC("license") = "GPL";
+int nr_del_errs;
+int test_pid;
+
+struct {
+ __uint(type, BPF_MAP_TYPE_INODE_STORAGE);
+ __uint(map_flags, BPF_F_NO_PREALLOC);
+ __type(key, int);
+ __type(value, long);
+} inode_map SEC(".maps");
+
+/* inode_storage_lookup is not an ideal hook for recursion tests, as it
+ * is static and more likely to get inlined. However, there isn't a
+ * better function for the test. This is because we need to call
+ * bpf_inode_storage_* helpers with an inode intput. Unlike task local
+ * storage, for which we can use bpf_get_current_task_btf() to get task
+ * pointer with BTF, for inode local storage, we need the get the inode
+ * pointer from function arguments. Other functions, such as,
+ * bpf_local_storage_get() does not take inode as input.
+ */
+SEC("fentry/inode_storage_lookup")
+int BPF_PROG(trace_inode_storage_lookup, struct inode *inode)
+{
+ struct task_struct *task = bpf_get_current_task_btf();
+ long *ptr;
+ int err;
+
+ if (!test_pid || task->pid != test_pid)
+ return 0;
+
+ /* This doesn't have BPF_LOCAL_STORAGE_GET_F_CREATE, so it will
+ * not trigger on the first call of bpf_inode_storage_get() below.
+ *
+ * This is called twice, recursion_misses += 2.
+ */
+ ptr = bpf_inode_storage_get(&inode_map, inode, 0, 0);
+ if (ptr) {
+ *ptr += 1;
+
+ /* This is called once, recursion_misses += 1. */
+ err = bpf_inode_storage_delete(&inode_map, inode);
+ if (err == -EBUSY)
+ nr_del_errs++;
+ }
+
+ return 0;
+}
+
+SEC("fentry/security_inode_mkdir")
+int BPF_PROG(trace_inode_mkdir, struct inode *dir,
+ struct dentry *dentry,
+ int mode)
+{
+ struct task_struct *task = bpf_get_current_task_btf();
+ long *ptr;
+
+ if (!test_pid || task->pid != test_pid)
+ return 0;
+
+ /* Trigger trace_inode_storage_lookup, the first time */
+ ptr = bpf_inode_storage_get(&inode_map, dir, 0,
+ BPF_LOCAL_STORAGE_GET_F_CREATE);
+
+ /* trace_inode_storage_lookup cannot get ptr, so *ptr is 0.
+ * Set ptr to 200.
+ */
+ if (ptr && !*ptr)
+ *ptr = 200;
+
+ /* Trigger trace_inode_storage_lookup, the second time.
+ * trace_inode_storage_lookup can now get ptr and increase the
+ * value. Now the value is 201.
+ */
+ bpf_inode_storage_get(&inode_map, dir, 0,
+ BPF_LOCAL_STORAGE_GET_F_CREATE);
+
+ return 0;
+
+}
--
2.43.5
More information about the Linux-security-module-archive
mailing list