+ selftests-mm-check-stat-return-value-in-khugepaged-get_finfo.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: selftests/mm: check stat() return value in khugepaged get_finfo()
has been added to the -mm mm-unstable branch.  Its filename is
     selftests-mm-check-stat-return-value-in-khugepaged-get_finfo.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-check-stat-return-value-in-khugepaged-get_finfo.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Anshuman <anshumantewari123@gmail.com>
Subject: selftests/mm: check stat() return value in khugepaged get_finfo()
Date: Wed, 19 Aug 2026 17:44:26 +0530

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.

Link: https://lore.kernel.org/20260819121426.49500-1-anshumantewari123@gmail.com
Signed-off-by: Anshuman <anshumantewari123@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/khugepaged.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/mm/khugepaged.c~selftests-mm-check-stat-return-value-in-khugepaged-get_finfo
+++ a/tools/testing/selftests/mm/khugepaged.c
@@ -124,7 +124,8 @@ 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,
_

Patches currently in -mm which might be from anshumantewari123@gmail.com are

selftests-mm-fix-unchecked-ftruncate-return-value-in-soft-dirty-test.patch
selftests-mm-check-stat-return-value-in-khugepaged-get_finfo.patch