Re: [PATCH v8 2/2] fs: ext4: Modify inode-test.c to use KUnit parameterized testing feature

[Marco Elver]

On Sun, 15 Nov 2020 at 19:59, Arpitha Raghunandan <98.arpi@xxxxxxxxx> wrote:
>
> Modify fs/ext4/inode-test.c to use the parameterized testing
> feature of KUnit.
>
> Signed-off-by: Arpitha Raghunandan <98.arpi@xxxxxxxxx>
> Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
> ---
> Changes v7->v8:
> - Replace strcpy() with strncpy() in timestamp_expectation_to_desc()
> Changes v6->v7:
> - Introduce timestamp_expectation_to_desc() to convert param to
>   description.
> Changes v5->v6:
> - No change to this patch of the patch series
> Changes v4->v5:
> - No change to this patch of the patch series
> Changes v3->v4:
> - Modification based on latest implementation of KUnit parameterized testing
> Changes v2->v3:
> - Marked hardcoded test data const
> - Modification based on latest implementation of KUnit parameterized testing
> Changes v1->v2:
> - Modification based on latest implementation of KUnit parameterized testing
>
>  fs/ext4/inode-test.c | 323 ++++++++++++++++++++++---------------------
>  1 file changed, 167 insertions(+), 156 deletions(-)
>
> diff --git a/fs/ext4/inode-test.c b/fs/ext4/inode-test.c
> index d62d802c9c12..2c0c00c45c6b 100644
> --- a/fs/ext4/inode-test.c
> +++ b/fs/ext4/inode-test.c
> @@ -80,6 +80,148 @@ struct timestamp_expectation {
>         bool lower_bound;
>  };
>
> +static const struct timestamp_expectation test_data[] = {
> +       {
> +               .test_case_name = LOWER_BOUND_NEG_NO_EXTRA_BITS_CASE,
> +               .msb_set = true,
> +               .lower_bound = true,
> +               .extra_bits = 0,
> +               .expected = {.tv_sec = -0x80000000LL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NEG_NO_EXTRA_BITS_CASE,
> +               .msb_set = true,
> +               .lower_bound = false,
> +               .extra_bits = 0,
> +               .expected = {.tv_sec = -1LL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = LOWER_BOUND_NONNEG_NO_EXTRA_BITS_CASE,
> +               .msb_set = false,
> +               .lower_bound = true,
> +               .extra_bits = 0,
> +               .expected = {0LL, 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NONNEG_NO_EXTRA_BITS_CASE,
> +               .msb_set = false,
> +               .lower_bound = false,
> +               .extra_bits = 0,
> +               .expected = {.tv_sec = 0x7fffffffLL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = LOWER_BOUND_NEG_LO_1_CASE,
> +               .msb_set = true,
> +               .lower_bound = true,
> +               .extra_bits = 1,
> +               .expected = {.tv_sec = 0x80000000LL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NEG_LO_1_CASE,
> +               .msb_set = true,
> +               .lower_bound = false,
> +               .extra_bits = 1,
> +               .expected = {.tv_sec = 0xffffffffLL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = LOWER_BOUND_NONNEG_LO_1_CASE,
> +               .msb_set = false,
> +               .lower_bound = true,
> +               .extra_bits = 1,
> +               .expected = {.tv_sec = 0x100000000LL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NONNEG_LO_1_CASE,
> +               .msb_set = false,
> +               .lower_bound = false,
> +               .extra_bits = 1,
> +               .expected = {.tv_sec = 0x17fffffffLL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = LOWER_BOUND_NEG_HI_1_CASE,
> +               .msb_set = true,
> +               .lower_bound = true,
> +               .extra_bits =  2,
> +               .expected = {.tv_sec = 0x180000000LL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NEG_HI_1_CASE,
> +               .msb_set = true,
> +               .lower_bound = false,
> +               .extra_bits = 2,
> +               .expected = {.tv_sec = 0x1ffffffffLL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = LOWER_BOUND_NONNEG_HI_1_CASE,
> +               .msb_set = false,
> +               .lower_bound = true,
> +               .extra_bits = 2,
> +               .expected = {.tv_sec = 0x200000000LL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NONNEG_HI_1_CASE,
> +               .msb_set = false,
> +               .lower_bound = false,
> +               .extra_bits = 2,
> +               .expected = {.tv_sec = 0x27fffffffLL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NONNEG_HI_1_NS_1_CASE,
> +               .msb_set = false,
> +               .lower_bound = false,
> +               .extra_bits = 6,
> +               .expected = {.tv_sec = 0x27fffffffLL, .tv_nsec = 1L},
> +       },
> +
> +       {
> +               .test_case_name = LOWER_BOUND_NONNEG_HI_1_NS_MAX_CASE,
> +               .msb_set = false,
> +               .lower_bound = true,
> +               .extra_bits = 0xFFFFFFFF,
> +               .expected = {.tv_sec = 0x300000000LL,
> +                            .tv_nsec = MAX_NANOSECONDS},
> +       },
> +
> +       {
> +               .test_case_name = LOWER_BOUND_NONNEG_EXTRA_BITS_1_CASE,
> +               .msb_set = false,
> +               .lower_bound = true,
> +               .extra_bits = 3,
> +               .expected = {.tv_sec = 0x300000000LL, .tv_nsec = 0L},
> +       },
> +
> +       {
> +               .test_case_name = UPPER_BOUND_NONNEG_EXTRA_BITS_1_CASE,
> +               .msb_set = false,
> +               .lower_bound = false,
> +               .extra_bits = 3,
> +               .expected = {.tv_sec = 0x37fffffffLL, .tv_nsec = 0L},
> +       }
> +};
> +
> +static void timestamp_expectation_to_desc(const struct timestamp_expectation *t,
> +                                         char *desc)
> +{
> +       int desc_length = strlen(t->test_case_name);
> +
> +       strncpy(desc, t->test_case_name, desc_length);
> +       desc[desc_length] = '\0';
> +}

This unfortunately won't prevent out-of-bounds accesses if the
description is longer than KUNIT_PARAM_DESC_SIZE.

With strncpy() we want to avoid copying more bytes than the
destination buffer can hold. This can be done by simply a
strncpy(desc, t->test_case_name, KUNIT_PARAM_DESC_SIZE). But,
strncpy() is unsafe in certain cases, too, so the kernel introduced
strscpy() -- see the note about strncpy() in
Documentation/process/deprecated.rst. Also have a look at the
documentation about str{n,l,s}cpy() in lib/string.c.

So, finally, what we want here is just 1 line:

    strscpy(desc, t->test_case_name, KUNIT_PARAM_DESC_SIZE);

Patch 1/2 looks fine though, so hopefully v9 will be final. :-)

Thanks,
-- Marco