linux-kernel - Re: [PATCH] selftests/mm: ksm_tests: skip when not run as root

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Message-Id: <20260110163704.7b5e1e10735113baa23f42ef@linux-foundation.org>
Date: Sat, 10 Jan 2026 16:37:04 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Sun Jian <sun.jian.kdev@...il.com>
Cc: Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, SeongJae Park
 <sj@...nel.org>
Subject: Re: [PATCH] selftests/mm: ksm_tests: skip when not run as root

On Fri,  9 Jan 2026 17:43:13 +0800 Sun Jian <sun.jian.kdev@...il.com> wrote:

> ksm_tests writes KSM sysfs knobs under /sys/kernel/mm/ksm, which requires
> root privileges. When run unprivileged, it fails with permission errors
> and reports FAIL, which is misleading.
> 
> Skip the test early when not run as root to avoid false failures.

Thanks.

When reissuing a patch it's nice to cc those individuals who commented
on previous versions.

> --- a/tools/testing/selftests/mm/ksm_tests.c
> +++ b/tools/testing/selftests/mm/ksm_tests.c
> @@ -766,6 +766,11 @@ int main(int argc, char *argv[])
>  	bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT;
>  	long size_MB = 0;
>  
> +	if (geteuid() != 0) {
> +		printf("# SKIP ksm_tests requires root privileges\n");
> +		return KSFT_SKIP;
> +	}
> +

lgtm.  selftests/ code performs this test in about 20 places already,
all different.  In the interests of consistency and code cleanliness,
perhaps some kind person will centralize this check in some fashion!