[PATCH bpf-next 8/8] selftests/bpf: Test user memory kfunc errors

[Jiri Olsa <jolsa@kernel.org>]

Test invalid copy arguments, zero-length mapping operations, partial copy
faults, and copying to read-only mappings. Verify that a failed unmap
leaves the mapping intact, and that non-sleepable programs and programs
without CAP_SYS_ADMIN cannot call bpf_user_mmap.

Assisted-by: Codex:GPT-6
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../selftests/bpf/prog_tests/user_mem.c       | 45 +++++++++++++++++++
 tools/testing/selftests/bpf/progs/user_mem.c  | 29 ++++++++++++
 2 files changed, 74 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/user_mem.c b/tools/testing/selftests/bpf/prog_tests/user_mem.c
index c87620e39abb..f3a35f8e005a 100644
--- a/tools/testing/selftests/bpf/prog_tests/user_mem.c
+++ b/tools/testing/selftests/bpf/prog_tests/user_mem.c
@@ -263,10 +263,49 @@ static void test_partial_copy_fault(struct user_mem *skel)
 		munmap((void *)addr, second_page_unmapped ? page_size : page_size * 2);
 }
 
+static void test_zero_length_mapping(struct user_mem *skel)
+{
+	skel->bss->map_len = 0;
+	skel->bss->map_prot = PROT_READ | PROT_WRITE;
+	skel->bss->action = USER_MEM_MMAP;
+	user_mem_trigger();
+
+	ASSERT_EQ(skel->bss->user_addr, (unsigned long)-EINVAL, "zero_length_mapping");
+}
+
+static void test_failed_unmap(struct user_mem *skel)
+{
+	long page_size = sysconf(_SC_PAGESIZE);
+	unsigned long addr = ~0UL;
+
+	if (!user_mem_mmap(skel, page_size, PROT_READ | PROT_WRITE, &addr))
+		return;
+
+	skel->bss->user_addr = addr;
+	skel->bss->map_len = 0;
+	skel->bss->action = USER_MEM_UNMAP;
+	user_mem_trigger();
+
+	if (ASSERT_EQ(skel->bss->ret, -EINVAL, "zero_length_unmap"))
+		check_user_mem_vma((void *)addr, page_size, "rw-p");
+
+	munmap((void *)addr, page_size);
+}
+
+static void test_invalid_copy(struct user_mem *skel)
+{
+	ASSERT_EQ(user_mem_copy(skel, 1, sizeof(data), 0), -EFAULT, "bad_copy");
+	ASSERT_EQ(user_mem_copy(skel, 1, sizeof(data), 1), -EINVAL, "bad_copy_flags");
+	ASSERT_EQ(user_mem_copy(skel, 1, 0, 0), 0, "zero_length_copy");
+	ASSERT_EQ(user_mem_copy(skel, 1, 0, 1), -EINVAL, "zero_length_copy_bad_flags");
+}
+
 void test_user_mem(void)
 {
 	struct user_mem *skel;
 
+	RUN_TESTS(user_mem);
+
 	skel = user_mem__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "open_and_load"))
 		return;
@@ -287,6 +326,12 @@ void test_user_mem(void)
 		test_copy_to_readonly_mapping(skel);
 	if (test__start_subtest("partial_copy_fault"))
 		test_partial_copy_fault(skel);
+	if (test__start_subtest("failed_unmap"))
+		test_failed_unmap(skel);
+	if (test__start_subtest("invalid_copy"))
+		test_invalid_copy(skel);
+	if (test__start_subtest("zero_length_mapping"))
+		test_zero_length_mapping(skel);
 
 out:
 	user_mem__destroy(skel);
diff --git a/tools/testing/selftests/bpf/progs/user_mem.c b/tools/testing/selftests/bpf/progs/user_mem.c
index 6ebfdc54edad..1ff5be6e3e62 100644
--- a/tools/testing/selftests/bpf/progs/user_mem.c
+++ b/tools/testing/selftests/bpf/progs/user_mem.c
@@ -80,3 +80,32 @@ int user_mem_test(struct pt_regs *ctx)
 
 	return 0;
 }
+
+SEC("?uprobe//proc/self/exe:user_mem_trigger")
+__failure
+__msg("program must be sleepable to call sleepable kfunc bpf_user_mmap")
+__msg("cannot be used in non-sleepable program")
+int user_mem_nonsleepable(struct pt_regs *ctx)
+{
+	bpf_user_mmap(4096, 1);
+	return 0;
+}
+
+SEC("?kprobe")
+__failure
+__msg("program must be sleepable to call sleepable kfunc bpf_user_mmap")
+__msg("cannot be used in non-sleepable program")
+int user_mem_kprobe(struct pt_regs *ctx)
+{
+	bpf_user_mmap(4096, 1);
+	return 0;
+}
+
+SEC("?uprobe.s//proc/self/exe:user_mem_trigger")
+__failure_unpriv __caps_unpriv(CAP_BPF | CAP_PERFMON)
+__msg_unpriv("calling kernel function bpf_user_mmap is not allowed")
+int user_mem_no_sysadmin(struct pt_regs *ctx)
+{
+	bpf_user_mmap(4096, 1);
+	return 0;
+}
-- 
2.54.0