Re: [PATCH 2/2] selftests, x86, pkeys: test with random, unallocated protection keys

[Kirill A. Shutemov]

On Thu, Feb 23, 2017 at 02:26:04PM -0800, Dave Hansen wrote:
> 
> 
> Shuah, I assume you'll take this patch in through the selftests tree.
> 
> --
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> 
> The kernel pkeys code had a minor bug where it did some large shifts
> to an integer which is undefined behavior in C.  It didn't cause any
> real harm, but it is screwy behavior that the kernel should have
> rejected.
> 
> Add a test case for this.
> 
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> ec: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Shuah Khan <shuah@xxxxxxxxxx>
> Cc: linux-kselftest@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: x86@xxxxxxxxxx
> ---
> 
>  b/tools/testing/selftests/x86/protection_keys.c |   25 ++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff -puN tools/testing/selftests/x86/protection_keys.c~pkeys-better-selftests-of-random-pkey tools/testing/selftests/x86/protection_keys.c
> --- a/tools/testing/selftests/x86/protection_keys.c~pkeys-better-selftests-of-random-pkey	2017-02-23 14:21:05.168391529 -0800
> +++ b/tools/testing/selftests/x86/protection_keys.c	2017-02-23 14:23:03.244671815 -0800
> @@ -1123,6 +1123,30 @@ void test_pkey_syscalls_on_non_allocated
>  }
>  
>  /* Assumes that all pkeys other than 'pkey' are unallocated */
> +void test_pkey_syscalls_on_non_allocated_random_pkey(int *ptr, u16 pkey)
> +{
> +	int err;
> +	int nr_tests = 0;
> +
> +	while (nr_tests < 1000) {
> +		int test_pkey = rand();

rand(3) doesn't generate negative numbers. Would be good to cover this
case too.

		int test_pkey = rand() - RAND_MAX/2;

?

Otherwise looks good to me.

-- 
 Kirill A. Shutemov