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

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Date:   Fri, 1 Sep 2023 12:18:31 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Reinette Chatre <reinette.chatre@...el.com>
cc:     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>,
        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

On Thu, 31 Aug 2023, Reinette Chatre wrote:

> 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.

Of course, I don't know why I added that - 1 there.

-- 
 i.