[PATCH] selftests/mm: check stat() return value in khugepaged get_finfo()

[Anshuman <anshumantewari123@gmail.com>]

get_finfo() calls stat() to get metadata about the target directory,
but never checks the return value. On failure, stat() returns -1 and
leaves path_stat unmodified, so path_stat.st_mode may contain
uninitialized stack data.

The code then checks S_ISDIR(path_stat.st_mode) against this
potentially garbage value. This can produce a misleading "Not a
directory" error when the real problem is a nonexistent or
inaccessible path, or, in the worst case, the check could pass by
chance on garbage data and let the function continue using an
invalid path_stat for the rest of its logic.

Check the return value and fail with a clear error message if
stat() fails, matching the error-handling style already used for
statfs() and read_file() later in the same function.

Signed-off-by: Anshuman <anshumantewari123@gmail.com>
---
 tools/testing/selftests/mm/khugepaged.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
index 10e8dedcb..2240a9b4f 100644
--- a/tools/testing/selftests/mm/khugepaged.c
+++ b/tools/testing/selftests/mm/khugepaged.c
@@ -121,7 +121,8 @@ static void get_finfo(const char *dir)
 	char *str, *end;
 
 	finfo.dir = dir;
-	stat(finfo.dir, &path_stat);
+	if (stat(finfo.dir, &path_stat))
+		ksft_exit_fail_perror("stat()");
 	if (!S_ISDIR(path_stat.st_mode))
 		ksft_exit_fail_msg("%s: Not a directory (%s)\n", __func__, finfo.dir);
 	if (snprintf(finfo.path, sizeof(finfo.path), "%s/" TEST_FILE,
-- 
2.55.0