Re: [PATCH bpf-next 3/3] bpf: Update LSM selftests for bpf_ima_inode_hash

[Yonghong Song <yhs@fb.com>]

On 11/20/20 5:17 AM, KP Singh wrote:
> From: KP Singh <kpsingh@google.com>
> 
> - Update the IMA policy before executing the test binary (this is not an
>    override of the policy, just an append that ensures that hashes are
>    calculated on executions).
> 
> - Call the bpf_ima_inode_hash in the bprm_committed_creds hook and check
>    if the call succeeded and a hash was calculated.
> 
> Signed-off-by: KP Singh <kpsingh@google.com>

LGTM with a few nits below.

Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   tools/testing/selftests/bpf/config            |  3 ++
>   .../selftests/bpf/prog_tests/test_lsm.c       | 32 +++++++++++++++++++
>   tools/testing/selftests/bpf/progs/lsm.c       |  7 +++-
>   3 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
> index 2118e23ac07a..4b5764031368 100644
> --- a/tools/testing/selftests/bpf/config
> +++ b/tools/testing/selftests/bpf/config
> @@ -39,3 +39,6 @@ CONFIG_BPF_JIT=y
>   CONFIG_BPF_LSM=y
>   CONFIG_SECURITY=y
>   CONFIG_LIRC=y
> +CONFIG_IMA=y
> +CONFIG_IMA_WRITE_POLICY=y
> +CONFIG_IMA_READ_POLICY=y
> diff --git a/tools/testing/selftests/bpf/prog_tests/test_lsm.c b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
> index 6ab29226c99b..3f5d64adb233 100644
> --- a/tools/testing/selftests/bpf/prog_tests/test_lsm.c
> +++ b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
> @@ -52,6 +52,28 @@ int exec_cmd(int *monitored_pid)
>   	return -EINVAL;
>   }
>   
[...]
> +
>   void test_test_lsm(void)
>   {
>   	struct lsm *skel = NULL;
> @@ -66,6 +88,10 @@ void test_test_lsm(void)
>   	if (CHECK(err, "attach", "lsm attach failed: %d\n", err))
>   		goto close_prog;
>   
> +	err = update_ima_policy();
> +	if (CHECK(err != 0, "update_ima_policy", "error = %d\n", err))
> +		goto close_prog;

"err != 0" => err?
"error = %d" => "err %d" for consistency with other usage in this function.

> +
>   	err = exec_cmd(&skel->bss->monitored_pid);
>   	if (CHECK(err < 0, "exec_cmd", "err %d errno %d\n", err, errno))
>   		goto close_prog;
> @@ -83,6 +109,12 @@ void test_test_lsm(void)
>   	CHECK(skel->bss->mprotect_count != 1, "mprotect_count",
>   	      "mprotect_count = %d\n", skel->bss->mprotect_count);
>   
> +	CHECK(skel->data->ima_hash_ret < 0, "ima_hash_ret",
> +	      "ima_hash_ret = %d\n", skel->data->ima_hash_ret);
> +
> +	CHECK(skel->bss->ima_hash == 0, "ima_hash",
> +	      "ima_hash = %lu\n", skel->bss->ima_hash);
> +
>   	syscall(__NR_setdomainname, &buf, -2L);
>   	syscall(__NR_setdomainname, 0, -3L);
>   	syscall(__NR_setdomainname, ~0L, -4L);
> diff --git a/tools/testing/selftests/bpf/progs/lsm.c b/tools/testing/selftests/bpf/progs/lsm.c
> index ff4d343b94b5..b0f9639e4b0a 100644
> --- a/tools/testing/selftests/bpf/progs/lsm.c
> +++ b/tools/testing/selftests/bpf/progs/lsm.c
> @@ -35,6 +35,8 @@ char _license[] SEC("license") = "GPL";
>   int monitored_pid = 0;
>   int mprotect_count = 0;
>   int bprm_count = 0;
> +int ima_hash_ret = -1;

The helper returns type "long", but "int" type here should be fine too.

> +u64 ima_hash = 0;
>   
>   SEC("lsm/file_mprotect")
>   int BPF_PROG(test_int_hook, struct vm_area_struct *vma,
> @@ -65,8 +67,11 @@ int BPF_PROG(test_void_hook, struct linux_binprm *bprm)
>   	__u32 key = 0;
>   	__u64 *value;
>   
> -	if (monitored_pid == pid)
> +	if (monitored_pid == pid) {
>   		bprm_count++;
> +		ima_hash_ret = bpf_ima_inode_hash(bprm->file->f_inode,
> +						  &ima_hash, sizeof(ima_hash));
> +	}
>   
>   	bpf_copy_from_user(args, sizeof(args), (void *)bprm->vma->vm_mm->arg_start);
>   	bpf_copy_from_user(args, sizeof(args), (void *)bprm->mm->arg_start);
>