From a243f7fb11fe67c59c5df079384b123e58edb814 Mon Sep 17 00:00:00 2001 From: Tzung-Bi Shih Date: Thu, 29 Jan 2026 14:37:31 +0000 Subject: [PATCH] revocable: Add KUnit test for provider lifetime races Add a test to verify that revocable_alloc() correctly handles race conditions where the provider is being released. The test covers three scenarios: 1. Allocating from a NULL provider. 2. Allocating from a provider that has been detached (pointer is NULL). 3. Allocating from a provider that is in the process of destruction (refcount is 0), simulating a race between revocable_alloc() and revocable_provider_release(). A way to run the test: $ ./tools/testing/kunit/kunit.py run \ --kconfig_add CONFIG_REVOCABLE_KUNIT_TEST=y \ --kconfig_add CONFIG_PROVE_LOCKING=y \ --kconfig_add CONFIG_DEBUG_KERNEL=y \ --kconfig_add CONFIG_DEBUG_INFO=y \ --kconfig_add CONFIG_DEBUG_INFO_DWARF5=y \ --kconfig_add CONFIG_KASAN=y \ --kconfig_add CONFIG_DETECT_HUNG_TASK=y \ --kconfig_add CONFIG_DEFAULT_HUNG_TASK_TIMEOUT="10" \ --arch=x86_64 --raw_output=all \ revocable_test Signed-off-by: Tzung-Bi Shih Link: https://patch.msgid.link/20260129143733.45618-3-tzungbi@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/base/revocable_test.c | 41 +++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/drivers/base/revocable_test.c b/drivers/base/revocable_test.c index 1622aae92fd3..7fc4d6a3dff6 100644 --- a/drivers/base/revocable_test.c +++ b/drivers/base/revocable_test.c @@ -14,9 +14,13 @@ * * - Try Access Macro: Same as "Revocation" but uses the * REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED(). + * + * - Provider Use-after-free: Verifies revocable_alloc() correctly handles + * race conditions where the provider is being released. */ #include +#include #include static void revocable_test_basic(struct kunit *test) @@ -127,11 +131,48 @@ static void revocable_test_try_access_macro2(struct kunit *test) revocable_free(rev); } +static void revocable_test_provider_use_after_free(struct kunit *test) +{ + struct revocable_provider __rcu *rp; + struct revocable_provider *old_rp; + void *real_res = (void *)0x12345678; + struct revocable *rev; + + rp = revocable_provider_alloc(real_res); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rp); + + rev = revocable_alloc(NULL); + KUNIT_EXPECT_PTR_EQ(test, rev, NULL); + + /* Simulate the provider has been freed. */ + old_rp = rcu_replace_pointer(rp, NULL, 1); + rev = revocable_alloc(rp); + KUNIT_EXPECT_PTR_EQ(test, rev, NULL); + rcu_replace_pointer(rp, old_rp, 1); + + struct { + struct srcu_struct srcu; + void __rcu *res; + struct kref kref; + struct rcu_head rcu; + } *rp_internal = (void *)rp; + + /* Simulate the provider is releasing. */ + refcount_set(&rp_internal->kref.refcount, 0); + rev = revocable_alloc(rp); + KUNIT_EXPECT_PTR_EQ(test, rev, NULL); + refcount_set(&rp_internal->kref.refcount, 1); + + revocable_provider_revoke(&rp); + KUNIT_EXPECT_PTR_EQ(test, unrcu_pointer(rp), NULL); +} + static struct kunit_case revocable_test_cases[] = { KUNIT_CASE(revocable_test_basic), KUNIT_CASE(revocable_test_revocation), KUNIT_CASE(revocable_test_try_access_macro), KUNIT_CASE(revocable_test_try_access_macro2), + KUNIT_CASE(revocable_test_provider_use_after_free), {} }; -- 2.47.3