Re: [PATCH 1/2] tests/qtest/xlnx-versal-trng-test.c: Drop use of variable length array

[Zhao Liu]

On Thu, Jan 25, 2024 at 05:32:10PM +0000, Peter Maydell wrote:
> Date: Thu, 25 Jan 2024 17:32:10 +0000
> From: Peter Maydell <peter.maydell@linaro.org>
> Subject: [PATCH 1/2] tests/qtest/xlnx-versal-trng-test.c: Drop use of
>  variable length array
> X-Mailer: git-send-email 2.34.1
> 
> This test program is the last use of any variable length array in the
> codebase.  If we can get rid of all uses of VLAs we can make the
> compiler error on new additions.  This is a defensive measure against
> security bugs where an on-stack dynamic allocation isn't correctly
> size-checked (e.g.  CVE-2021-3527).
> 
> In this case the test code didn't even want a variable-sized
> array, it was just accidentally using syntax that gave it one.
> (The array size for C has to be an actual constant expression,
> not just something that happens to be known to be constant...)
> 
> Remove the VLA usage.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  tests/qtest/xlnx-versal-trng-test.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>

> 
> diff --git a/tests/qtest/xlnx-versal-trng-test.c 
> b/tests/qtest/xlnx-versal-trng-test.c
> index cef4e575bba..ba86f39d13c 100644
> --- a/tests/qtest/xlnx-versal-trng-test.c
> +++ b/tests/qtest/xlnx-versal-trng-test.c
> @@ -298,10 +298,13 @@ static size_t trng_collect(uint32_t *rnd, size_t cnt)
>      return i;
>  }
>  
> +/* These tests all generate 512 bits of random data with the device */
> +#define TEST_DATA_WORDS (512 / 32)
> +
>  static void trng_test_autogen(void)
>  {
> -    const size_t cnt = 512 / 32;
> -    uint32_t rng[cnt], prng[cnt];
> +    const size_t cnt = TEST_DATA_WORDS;
> +    uint32_t rng[TEST_DATA_WORDS], prng[TEST_DATA_WORDS];
>      size_t n;
>  
>      trng_reset();
> @@ -343,8 +346,8 @@ static void trng_test_autogen(void)
>  
>  static void trng_test_oneshot(void)
>  {
> -    const size_t cnt = 512 / 32;
> -    uint32_t rng[cnt];
> +    const size_t cnt = TEST_DATA_WORDS;
> +    uint32_t rng[TEST_DATA_WORDS];
>      size_t n;
>  
>      trng_reset();
> @@ -370,8 +373,8 @@ static void trng_test_oneshot(void)
>  
>  static void trng_test_per_str(void)
>  {
> -    const size_t cnt = 512 / 32;
> -    uint32_t rng[cnt], prng[cnt];
> +    const size_t cnt = TEST_DATA_WORDS;
> +    uint32_t rng[TEST_DATA_WORDS], prng[TEST_DATA_WORDS];
>      size_t n;
>  
>      trng_reset();
> @@ -415,8 +418,8 @@ static void trng_test_forced_prng(void)
>      const char *prop = "forced-prng";
>      const uint64_t seed = 0xdeadbeefbad1bad0ULL;
>  
> -    const size_t cnt = 512 / 32;
> -    uint32_t rng[cnt], prng[cnt];
> +    const size_t cnt = TEST_DATA_WORDS;
> +    uint32_t rng[TEST_DATA_WORDS], prng[TEST_DATA_WORDS];
>      size_t n;
>  
>      trng_reset();
> -- 
> 2.34.1
> 
>