linux-kernel - [PATCH v2] kunit: test_dev_action: Correctly cast 'priv' pointer to long*

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Message-ID: <20251017092814.80022-1-florian.schmaus@codasip.com>
Date: Fri, 17 Oct 2025 11:28:14 +0200
From: Florian Schmaus <florian.schmaus@...asip.com>
To: Brendan Higgins <brendan.higgins@...ux.dev>,
	David Gow <davidgow@...gle.com>,
	Rae Moar <rmoar@...gle.com>
Cc: linux-kselftest@...r.kernel.org,
	kunit-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	Florian Schmaus <florian.schmaus@...asip.com>
Subject: [PATCH v2] kunit: test_dev_action: Correctly cast 'priv' pointer to long*

The previous implementation incorrectly assumed the original type of
'priv' was void**, leading to an unnecessary and misleading
cast. Correct the cast of the 'priv' pointer in test_dev_action() to
its actual type, long*, removing an unnecessary cast.

As an additional benefit, this fixes an out-of-bounds CHERI fault on
hardware with architectural capabilities. The original implementation
tried to store a capability-sized pointer using the priv
pointer. However, the priv pointer's capability only granted access to
the memory region of its original long type, leading to a bounds
violation since the size of a long is smaller than the size of a
capability. This change ensures that the pointer usage respects the
capabilities' bounds.

Fixes: d03c720e03bd ("kunit: Add APIs for managing devices")
Reviewed-by: David Gow <davidgow@...gle.com>
Signed-off-by: Florian Schmaus <florian.schmaus@...asip.com>
---

Changes since v1:
    - Fix simple formatting issue: long* -> long *
	- Add 'Fixes' git trailer

 lib/kunit/kunit-test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c
index 8c01eabd4eaf..63130a48e237 100644
--- a/lib/kunit/kunit-test.c
+++ b/lib/kunit/kunit-test.c
@@ -739,7 +739,7 @@ static struct kunit_case kunit_current_test_cases[] = {

 static void test_dev_action(void *priv)
 {
-	*(void **)priv = (void *)1;
+	*(long *)priv = 1;
 }

 static void kunit_device_test(struct kunit *test)
-- 
2.51.0