selftests/mm: check for YAMA ptrace_scope configuraiton before modifying it

When running the memfd_secret test run_vmtests.sh unconditionally tries
to confgiure the YAMA LSM's ptrace_scope configuration, leading to an error
if YAMA is not in the running kernel:

# ./run_vmtests.sh: line 432: /proc/sys/kernel/yama/ptrace_scope: No such file or directory
# # ----------------------
# # running ./memfd_secret
# # ----------------------

Check that this file is present before trying to write to it.

The indentation here is a bit odd, and it doesn't seem great that we
configure but don't restore ptrace_scope.

Link: https://lkml.kernel.org/r/20250610-selftest-mm-enable-yama-v1-1-0097b6713116@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index dddd1dd8af145005737f4b903bd418b84c85f639..33fc7fafa8f9aea1201267f98636c43268ad64e7 100755 (executable)
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -429,7 +429,9 @@ CATEGORY="vma_merge" run_test ./merge
 
 if [ -x ./memfd_secret ]
 then
-(echo 0 > /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
+if [ -f /proc/sys/kernel/yama/ptrace_scope ]; then
+       (echo 0 > /proc/sys/kernel/yama/ptrace_scope 2>&1) | tap_prefix
+fi
 CATEGORY="memfd_secret" run_test ./memfd_secret
 fi