linux-kernel - Re: [PATCH v4 1/8] selftests/resctrl: Ensure the benchmark commands fits to its array

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Message-ID: <da9c1d88-73ea-b169-909c-e6e59e87c474@intel.com>
Date:   Thu, 31 Aug 2023 14:25:03 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        <linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>,
        Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
        Shaopeng Tan <tan.shaopeng@...fujitsu.com>
CC:     Fenghua Yu <fenghua.yu@...el.com>, Babu Moger <babu.moger@....com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/8] selftests/resctrl: Ensure the benchmark commands
 fits to its array

Hi Ilpo,

On 8/31/2023 4:08 AM, Ilpo Järvinen wrote:
> Benchmark command is copied into an array in the stack. The array is
> BENCHMARK_ARGS items long but the command line could try to provide a
> longer command. Argument size is also fixed by BENCHMARK_ARG_SIZE (63
> bytes of space after fitting the terminating \0 character) and user
> could have inputted argument longer than that.
> 
> Return error in case the benchmark command does not fit to the space
> allocated for it.
> 
> Fixes: ecdbb911f22d ("selftests/resctrl: Add MBM test")
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> ---
>  tools/testing/selftests/resctrl/resctrl_tests.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/testing/selftests/resctrl/resctrl_tests.c b/tools/testing/selftests/resctrl/resctrl_tests.c
> index d511daeb6851..a9331b31c32d 100644
> --- a/tools/testing/selftests/resctrl/resctrl_tests.c
> +++ b/tools/testing/selftests/resctrl/resctrl_tests.c
> @@ -255,9 +255,14 @@ int main(int argc, char **argv)
>  		return ksft_exit_skip("Not running as root. Skipping...\n");
>  
>  	if (has_ben) {
> +		if (argc - ben_ind >= BENCHMARK_ARGS)
> +			ksft_exit_fail_msg("Too long benchmark command.\n");
> +
>  		/* Extract benchmark command from command line. */
>  		for (i = ben_ind; i < argc; i++) {
>  			benchmark_cmd[i - ben_ind] = benchmark_cmd_area[i];
> +			if (strlen(argv[i]) >= BENCHMARK_ARG_SIZE - 1)

Should this perhaps be:
	if (strlen(argv[i]) >= BENCHMARK_ARG_SIZE)

As you note in the longest string that can be fitted should be 63 to account for
the \0. If I understand correctly comparing with "BENCHMARK_ARG_SIZE - 1" would
would consider a 63 byte string as invalid.
	

> +				ksft_exit_fail_msg("Too long benchmark command argument.\n");
>  			sprintf(benchmark_cmd[i - ben_ind], "%s", argv[i]);
>  		}
>  		benchmark_cmd[ben_count] = NULL;

Reinette