[PATCH bpf-next v9 5/5] selftests/bpf: Test mm_struct user memory kfuncs with linux_binprm

[Anastasios Papagiannis]

Add a sleepable BPF LSM program attached to bprm_check_security to test
bpf_copy_from_user_mm() and bpf_copy_from_user_mm_str().

Starting at bprm->p, verify that bpf_copy_from_user_mm() can copy the
contiguous NUL-separated argument and environment data. Then use
bpf_copy_from_user_mm_str() to read each argument and environment string
separately, advancing the offset by the length returned from each call.

Signed-off-by: Anastasios Papagiannis <tasos.papagiannnis@xxxxxxxxx>
---
 .../bpf/prog_tests/copy_from_user_bprm.c      | 65 +++++++++++++++++
 .../selftests/bpf/progs/copy_from_user_bprm.c | 69 +++++++++++++++++++
 2 files changed, 134 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c
 create mode 100644 tools/testing/selftests/bpf/progs/copy_from_user_bprm.c

diff --git a/tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c b/tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c
new file mode 100644
index 000000000000..310370689427
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/copy_from_user_bprm.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <errno.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <test_progs.h>
+
+#include "copy_from_user_bprm.skel.h"
+
+void test_copy_from_user_bprm(void)
+{
+	char data[] = "first\0second-argument\0SOME_ENV=a\0OTHER_ENV=something";
+	char arg0[] = "first";
+	char arg1[] = "second-argument";
+	char env0[] = "SOME_ENV=a";
+	char env1[] = "OTHER_ENV=something";
+	struct copy_from_user_bprm *skel;
+	pid_t child;
+	int status;
+
+	skel = copy_from_user_bprm__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_and_load"))
+		return;
+
+	if (!ASSERT_OK(copy_from_user_bprm__attach(skel), "attach"))
+		goto out;
+
+	child = fork();
+	if (!ASSERT_GE(child, 0, "fork"))
+		goto out;
+
+	if (!child) {
+		char *const argv[] = { arg0, arg1, NULL };
+		char *const envp[] = { env0, env1, NULL };
+
+		skel->bss->monitored_pid = getpid();
+		execvpe("true", argv, envp);
+		_exit(errno);
+	}
+
+	if (!ASSERT_EQ(waitpid(child, &status, 0), child, "waitpid"))
+		goto out;
+
+	if (ASSERT_TRUE(WIFEXITED(status), "child_exited"))
+		ASSERT_EQ(WEXITSTATUS(status), EPERM, "exec_errno");
+
+	ASSERT_EQ(skel->bss->bprm_argc, 2, "bprm_argc");
+	ASSERT_EQ(skel->bss->bprm_envc, 2, "bprm_envc");
+	ASSERT_EQ(skel->bss->data_len, sizeof(data), "data_len");
+	ASSERT_EQ(skel->bss->invalid_flags_ret, -EINVAL, "invalid_flags_ret");
+	ASSERT_EQ(skel->bss->copy_ret, 0, "copy_ret");
+	ASSERT_EQ(skel->bss->arg0_ret, sizeof(arg0), "arg0_ret");
+	ASSERT_EQ(skel->bss->arg1_ret, sizeof(arg1), "arg1_ret");
+	ASSERT_EQ(skel->bss->env0_ret, sizeof(env0), "env0_ret");
+	ASSERT_EQ(skel->bss->env1_ret, sizeof(env1), "env1_ret");
+	ASSERT_EQ(memcmp(skel->bss->data, data, sizeof(data)), 0, "data");
+	ASSERT_EQ(memcmp(skel->bss->arg0, arg0, sizeof(arg0)), 0, "arg0");
+	ASSERT_EQ(memcmp(skel->bss->arg1, arg1, sizeof(arg1)), 0, "arg1");
+	ASSERT_EQ(memcmp(skel->bss->env0, env0, sizeof(env0)), 0, "env0");
+	ASSERT_EQ(memcmp(skel->bss->env1, env1, sizeof(env1)), 0, "env1");
+
+out:
+	copy_from_user_bprm__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/copy_from_user_bprm.c b/tools/testing/selftests/bpf/progs/copy_from_user_bprm.c
new file mode 100644
index 000000000000..00ecba3ea567
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/copy_from_user_bprm.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <errno.h>
+
+char _license[] SEC("license") = "GPL";
+
+int monitored_pid;
+int bprm_argc;
+int bprm_envc;
+int data_len;
+int invalid_flags_ret;
+int copy_ret;
+int arg0_ret;
+int arg1_ret;
+int env0_ret;
+int env1_ret;
+char data[64] = {};
+char arg0[32] = {};
+char arg1[32] = {};
+char env0[32] = {};
+char env1[32] = {};
+
+SEC("lsm.s/bprm_check_security")
+int BPF_PROG(check_exec_args, struct linux_binprm *bprm)
+{
+	u32 pid = bpf_get_current_pid_tgid() >> 32;
+	struct mm_struct *mm;
+	u64 offset = 0;
+
+	if (pid != monitored_pid)
+		return 0;
+
+	mm = bprm->mm;
+	if (!mm)
+		return 0;
+
+	bprm_argc = bprm->argc;
+	bprm_envc = bprm->envc;
+
+	/* this is the total size of args and envs starting from bprm->p */
+	data_len = bprm->exec - bprm->p;
+
+	invalid_flags_ret = bpf_copy_from_user_mm(data, sizeof(data), (void *)bprm->p, mm, ~0ULL);
+
+	copy_ret = bpf_copy_from_user_mm(data, sizeof(data), (void *)bprm->p, mm, 0);
+	if (copy_ret)
+		return 0;
+
+	/* arg0 is at bprm->p */
+	arg0_ret = bpf_copy_from_user_mm_str(arg0, sizeof(arg0), (void *)(bprm->p + offset), mm, BPF_F_PAD_ZEROS);
+	offset += arg0_ret;
+
+	/* arg1 is at bprm->p + arg0_ret */
+	arg1_ret = bpf_copy_from_user_mm_str(arg1, sizeof(arg1), (void *)(bprm->p + offset), mm, BPF_F_PAD_ZEROS);
+	offset += arg1_ret;
+
+	/* env0 is at bprm->p + arg0_ret + arg1_ret */
+	env0_ret = bpf_copy_from_user_mm_str(env0, sizeof(env0), (void *)(bprm->p + offset), mm, BPF_F_PAD_ZEROS);
+	offset += env0_ret;
+
+	/* env1 is at bprm->p + arg0_ret + arg1_ret + env0_ret */
+	env1_ret = bpf_copy_from_user_mm_str(env1, sizeof(env1), (void *)(bprm->p + offset), mm, BPF_F_PAD_ZEROS);
+
+	return -EPERM;
+}
-- 
2.55.0