[PATCH bpf-next 2/2] selftests/bpf: Update ima test helper's mount uuid logic

[KP Singh]

Oops I sent this to the wrong list. Sorry about that.

On Tue, Dec 1, 2020 at 3:32 PM KP Singh <kpsingh at chromium.org> wrote:
>
> From: KP Singh <kpsingh at google.com>
>
> The test uses blkid to determine the uuid which may not be available on
> every system. Switch the logic to a good-old for loop iterating over
> /dev/disk/by-uuid and reading the symlinks to find the correct UUID for
> a given loop device
>
> Fixes: 34b82d3ac105 ("bpf: Add a selftest for bpf_ima_inode_hash")
> Signed-off-by: KP Singh <kpsingh at google.com>
> ---
>  tools/testing/selftests/bpf/ima_setup.sh | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/ima_setup.sh b/tools/testing/selftests/bpf/ima_setup.sh
> index ed29bde26a12..7b8615c30c09 100755
> --- a/tools/testing/selftests/bpf/ima_setup.sh
> +++ b/tools/testing/selftests/bpf/ima_setup.sh
> @@ -31,8 +31,24 @@ setup()
>          mount "${loop_device}" "${mount_dir}"
>
>          cp "${TEST_BINARY}" "${mount_dir}"
> -        local mount_uuid="$(blkid -s UUID -o value ${loop_device})"
> -        echo "measure func=BPRM_CHECK fsuuid=${mount_uuid}" > ${IMA_POLICY_FILE}
> +        local mount_uuid=""
> +        # This can be done with blkid -s UUID -o value ${loop_device} but
> +        # blkid might not be available everywhere, especially in busybox
> +        # environments.
> +        for uuid in $(ls /dev/disk/by-uuid); do
> +                local link_target="$(readlink -f /dev/disk/by-uuid/${uuid})"
> +                if [[ "${loop_device}" == "${link_target}" ]]; then
> +                        mount_uuid="${uuid}"
> +                        break;
> +                fi
> +        done
> +
> +        if [[ -z "${mount_uuid}" ]]; then
> +                echo "Could not find mount_uuid for ${loop_device}"
> +                exit 1;
> +        fi
> +
> +        echo "measure func=BPRM_CHECK fsuuid=${mount_uuid:?}" > ${IMA_POLICY_FILE}
>  }
>
>  cleanup() {
> --
> 2.29.2.454.gaff20da3a2-goog
>