[PATCH v6 9/9] selftests/ftrace: Walk up to find test.d/functions when a subdirectory is passed

[wen.yang@linux.dev]

From: Wen Yang <wen.yang@linux.dev>

When a test directory that does not itself contain test.d/functions is
passed to ftracetest (e.g. verification/test.d/tlob/), ftracetest fell
back to its own functions file and lost the rv-specific check_requires
handling for ':monitor' and ':reactor' requirements.

Walk up the directory tree from OPT_TEST_DIR until a directory containing
test.d/functions is found. This allows monitor subdirectories to be passed
directly as the test root without placing a functions shim in each one.

The RV verification suite uses this so that

  tools/testing/selftests/verification/test.d/tlob/run_tlob_tests.sh

can pass test.d/tlob/ to ftracetest and have it source
verification/test.d/functions (which understands ':monitor'/':reactor').

Suggested-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Wen Yang <wen.yang@linux.dev>
---
 tools/testing/selftests/ftrace/ftracetest | 26 ++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/ftrace/ftracetest b/tools/testing/selftests/ftrace/ftracetest
index 0a56bf209f6c..8f9d9291bf4c 100755
--- a/tools/testing/selftests/ftrace/ftracetest
+++ b/tools/testing/selftests/ftrace/ftracetest
@@ -159,9 +159,29 @@ parse_opts() { # opts
   if [ -n "$OPT_TEST_CASES" ]; then
     TEST_CASES=$OPT_TEST_CASES
   fi
-  if [ -n "$OPT_TEST_DIR" -a -f "$OPT_TEST_DIR"/test.d/functions ]; then
-    TOP_DIR=$OPT_TEST_DIR
-    TEST_DIR=$TOP_DIR/test.d
+  if [ -n "$OPT_TEST_DIR" ]; then
+    # Walk up from OPT_TEST_DIR to find the nearest ancestor that contains
+    # test.d/functions.  This allows a monitor subdirectory (e.g.
+    # verification/test.d/tlob/) to be passed directly without placing a
+    # dummy functions shim in each new subdirectory.
+    # Security: only walk within directories owned by root or the current user
+    # to prevent sourcing a functions file planted in a world-writable ancestor.
+    dir=$(realpath "$OPT_TEST_DIR" 2>/dev/null || echo "$OPT_TEST_DIR")
+    while [ "$dir" != "/" ] && [ "$dir" != "//" ]; do
+      if [ -f "$dir/test.d/functions" ]; then
+        # Verify the directory is not world-writable to prevent LPE.
+        dirperms=$(stat -c "%a" "$dir" 2>/dev/null || stat -f "%Lp" "$dir" 2>/dev/null)
+        case "$dirperms" in
+          *2|*3|*6|*7) ;; # world-writable: skip this candidate
+          *)
+            TOP_DIR=$dir
+            TEST_DIR=$TOP_DIR/test.d
+            break
+            ;;
+        esac
+      fi
+      dir=$(dirname "$dir")
+    done
   fi
 }
 
-- 
2.25.1