linux-kernel - [PATCH 2/6] selftests/mm: Fix assumption that sudo is present

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Message-ID: <20250220-mm-selftests-v1-2-9bbf57d64463@google.com>
Date: Thu, 20 Feb 2025 15:03:14 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Shuah Khan <shuah@...nel.org>
Cc: Mateusz Guzik <mjguzik@...il.com>, linux-mm@...ck.org, linux-kselftest@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Brendan Jackman <jackmanb@...gle.com>
Subject: [PATCH 2/6] selftests/mm: Fix assumption that sudo is present

If we are root, sudo isn't needed. If we are not root, we need sudo, so
skip the test if it isn't present.

We already do this for on-fault-limit, but this uses separate
infrastructure since that is specifically for sudo-ing to the nobody
user.

Note this ptrace_skip configuration still fails if that file doesn't
exist, but in that case the test is still fine, so this just prints an
error but doesn't break anything. I suspect that's probably deliberate.

Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index da7e266681031d2772fb0c4139648904a18e0bf9..9c963f50927ab2b10c3f942cedd087087d4d0def 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -89,6 +89,17 @@ RUN_ALL=false
 RUN_DESTRUCTIVE=false
 TAP_PREFIX="# "
 
+# We can do stuff as root either if we are already root, or if sudo exists.
+if [ "$(id -u)" == 0 ]; then
+	HAVE_SUDO_ROOT=true
+	SUDO_ROOT=
+elif command -v sudo >/dev/null 2>&1; then
+	HAVE_SUDO_ROOT=true
+	SUDO_ROOT=sudo
+else
+	HAVE_SUDO_ROOT=false
+fi
+
 while getopts "aht:n" OPT; do
 	case ${OPT} in
 		"a") RUN_ALL=true ;;
@@ -384,10 +395,13 @@ CATEGORY="madv_guard" run_test ./guard-pages
 # MADV_POPULATE_READ and MADV_POPULATE_WRITE tests
 CATEGORY="madv_populate" run_test ./madv_populate
 
-if [ -x ./memfd_secret ]
-then
-(echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
-CATEGORY="memfd_secret" run_test ./memfd_secret
+if [ -x ./memfd_secret ]; then
+	if $HAVE_SUDO_ROOT; then
+		(echo 0 | $SUDO_ROOT tee /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
+		CATEGORY="memfd_secret" run_test ./memfd_secret
+	else
+		echo "# SKIP ./memfd_secret"
+	fi
 fi
 
 # KSM KSM_MERGE_TIME_HUGE_PAGES test with size of 100

-- 
2.48.1.601.g30ceb7b040-goog