* [PATCH for-v7.5 03/14] kasan: Avoid an unrelated RCU warning in the callback test
[not found] <20261113005747.2977123-1-jfern@kernel.org>
@ 2026-11-13 0:57 ` Joel Fernandes
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From: Joel Fernandes @ 2026-11-13 0:57 UTC (permalink / raw)
To: linux-kernel, Paul E . McKenney, Frederic Weisbecker,
Neeraj Upadhyay, Joel Fernandes, Josh Triplett, Boqun Feng,
Uladzislau Rezki, Steven Rostedt, Mathieu Desnoyers,
Lai Jiangshan, Zqiang, Andrey Ryabinin, Alexander Potapenko,
Andrey Konovalov, Dmitry Vyukov, Vincenzo Frascino, Andrew Morton
Cc: rcu, kasan-dev, linux-mm
rcu_uaf() passes a false protection condition to
rcu_dereference_protected(), which produces a suspicious-RCU-usage
warning before the intended KASAN failure occurs.
The pointer refers to a fresh allocation that has not been published to
readers. State that protection condition explicitly, leaving the intended
tests intact.
Test:
Built with CONFIG_KASAN_KUNIT_TEST=m
Booted Qemu guest (8 CPUs), ran modprobe kasan_test filtered to kasan.*rcu_uaf*
Signed-off-by: Joel Fernandes <jfern@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
---
mm/kasan/kasan_test_c.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c
index b9e167ed5be3..4e23765d722c 100644
--- a/mm/kasan/kasan_test_c.c
+++ b/mm/kasan/kasan_test_c.c
@@ -967,8 +967,9 @@ static void rcu_uaf(struct kunit *test)
ptr = kmalloc_obj(struct kasan_rcu_info);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
+ /* The freshly allocated object has not been published to readers. */
global_rcu_ptr = rcu_dereference_protected(
- (struct kasan_rcu_info __rcu *)ptr, NULL);
+ (struct kasan_rcu_info __rcu *)ptr, true);
KUNIT_EXPECT_KASAN_FAIL_READ(test,
call_rcu(&global_rcu_ptr->rcu, rcu_uaf_reclaim);
--
2.54.0
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