Re: [PATCH V4] tools/testing/selftests/sysctl: Add pre-check to the value of writes_strict

[Kees Cook]

On Mon, Jun 26, 2017 at 5:52 PM, Orson Zhai <orson.zhai@xxxxxxxxxx> wrote:
> Sysctl test will fail in some items if the value of /proc/sys/kernel
> /sysctrl_writes_strict is 0 as the default value in kernel older than v4.5.
>
> Make this test more robus and compatible with older kernel by checking and
> update writes_strict value and restore it when test is done.
>
> Signed-off-by: Orson Zhai <orson.zhai@xxxxxxxxxx>
> Reviewed-by: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> Tested-by: Sumit Semwal <sumit.semwal@xxxxxxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

Thanks!

-Kees

> ---
>  tools/testing/selftests/sysctl/common_tests     | 22 ++++++++++++++++++++++
>  tools/testing/selftests/sysctl/run_numerictests |  2 +-
>  tools/testing/selftests/sysctl/run_stringtests  |  2 +-
>  3 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/sysctl/common_tests b/tools/testing/selftests/sysctl/common_tests
> index 17d534b1b7b4..b6862322962f 100644
> --- a/tools/testing/selftests/sysctl/common_tests
> +++ b/tools/testing/selftests/sysctl/common_tests
> @@ -24,6 +24,14 @@ verify()
>         return 0
>  }
>
> +exit_test()
> +{
> +       if [ ! -z ${old_strict} ]; then
> +               echo ${old_strict} > ${WRITES_STRICT}
> +       fi
> +       exit $rc
> +}
> +
>  trap 'set_orig; rm -f "${TEST_FILE}"' EXIT
>
>  rc=0
> @@ -63,6 +71,20 @@ else
>         echo "ok"
>  fi
>
> +echo -n "Checking write strict setting ... "
> +WRITES_STRICT="${SYSCTL}/kernel/sysctl_writes_strict"
> +if [ ! -e ${WRITES_STRICT} ]; then
> +       echo "FAIL, but skip in case of old kernel" >&2
> +else
> +       old_strict=$(cat ${WRITES_STRICT})
> +       if [ "$old_strict" = "1" ]; then
> +               echo "ok"
> +       else
> +               echo "FAIL, strict value is 0 but force to 1 to continue" >&2
> +               echo "1" > ${WRITES_STRICT}
> +       fi
> +fi
> +
>  # Now that we've validated the sanity of "set_test" and "set_orig",
>  # we can use those functions to set starting states before running
>  # specific behavioral tests.
> diff --git a/tools/testing/selftests/sysctl/run_numerictests b/tools/testing/selftests/sysctl/run_numerictests
> index 8510f93f2d14..e6e76c93d948 100755
> --- a/tools/testing/selftests/sysctl/run_numerictests
> +++ b/tools/testing/selftests/sysctl/run_numerictests
> @@ -7,4 +7,4 @@ TEST_STR=$(( $ORIG + 1 ))
>
>  . ./common_tests
>
> -exit $rc
> +exit_test
> diff --git a/tools/testing/selftests/sysctl/run_stringtests b/tools/testing/selftests/sysctl/run_stringtests
> index 90a9293d520c..857ec667fb02 100755
> --- a/tools/testing/selftests/sysctl/run_stringtests
> +++ b/tools/testing/selftests/sysctl/run_stringtests
> @@ -74,4 +74,4 @@ else
>         echo "ok"
>  fi
>
> -exit $rc
> +exit_test
> --
> 2.12.2
>



-- 
Kees Cook
Pixel Security