Re: [PATCH] selftests/mm: check strdup() and fix buf leak in parse_test_type()

["David Hildenbrand (Arm)" <david@kernel.org>]

On 8/21/26 13:44, Anshuman wrote:
> The return value of strdup() is never checked before being passed to
> strsep() and strcmp(). If strdup() fails and returns NULL, strsep()
> returns NULL as well, and the subsequent strcmp(NULL, "all") is
> undefined behavior, likely causing a crash.

In practice this is extraordinarily unlikely to ever fail. :)

So I don't think we would ever experience this.

> 
> Additionally, buf is never freed. strsep() advances the buf pointer
> past the first token, so by the time buf would normally be freed,
> the original pointer returned by strdup() has already been
> overwritten and is no longer available.

Given that parse_test_type() is called only once, nobody cares.

> 
> Check strdup()'s return value and fail cleanly on allocation failure.
> Keep a separate pointer to the original allocation so it can be
> freed once buf is done being used, after all parsing has completed
> successfully.
> 
> Signed-off-by: Anshuman <anshumantewari123@gmail.com>
> ---

[...]
That's too much churn for something that is irrelevant in practice and
makes the code more complicated.

So the following is better I think:

From 36d525409eb16f56e667b2f979f2c6ef112ff235 Mon Sep 17 00:00:00 2001
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: Fri, 21 Aug 2026 15:57:57 +0200
Subject: [PATCH] selftests/mm: khugepaged: remove str_dup() usage

We don't check str_dup() return value and never free it. While both
things are irrelevant in practice, let's just work on argv[0] directly
and avoid the str_dup().

Nobody after us needs these parts of the argv[0] string.

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 tools/testing/selftests/mm/khugepaged.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/khugepaged.c
b/tools/testing/selftests/mm/khugepaged.c
index d3a53673e1f9..7520fc0483ac 100644
--- a/tools/testing/selftests/mm/khugepaged.c
+++ b/tools/testing/selftests/mm/khugepaged.c
@@ -1226,7 +1226,7 @@ static void parse_test_type(int argc, char **argv)
 		return;
 	}
 -	buf = strdup(argv[0]);
+	buf = argv[0];
 	token = strsep(&buf, ":");
  	if (!strcmp(token, "all")) {
-- 
2.43.0


-- 
Cheers,

David