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From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>
To: Brendan Higgins <brendanhiggins@google.com>,
	David Gow <davidgow@google.com>,
	Rae Moar <rmoar@google.com>,
	Shuah Khan <skhan@linuxfoundation.org>
Cc: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= <mic@digikod.net>,
	Alan Maguire <alan.maguire@oracle.com>,
	Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Ingo Molnar <mingo@redhat.com>,
	James Morris <jamorris@linux.microsoft.com>,
	Kees Cook <keescook@chromium.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	"Madhavan T . Venkataraman" <madvenka@linux.microsoft.com>,
	Marco Pagani <marpagan@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Thara Gopinath <tgopinath@microsoft.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Zahra Tarkhani <ztarkhani@microsoft.com>,
	kvm@vger.kernel.org,
	linux-hardening@vger.kernel.org,
	linux-hyperv@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-um@lists.infradead.org,
	x86@kernel.org
Subject: [PATCH v4 2/7] kunit: Fix kthread reference
Date: Tue, 26 Mar 2024 10:51:13 +0100
Message-ID: <20240326095118.126696-3-mic@digikod.net>
In-Reply-To: <20240326095118.126696-1-mic@digikod.net>
References: <20240326095118.126696-1-mic@digikod.net>
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There is a race condition when a kthread finishes after the deadline and
before the call to kthread_stop(), which may lead to use after free.

Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Fixes: adf505457032 ("kunit: fix UAF when run kfence test case test_gfpzero")
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Rae Moar <rmoar@google.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20240326095118.126696-3-mic@digikod.net
---

Changes since v2:
* Add Fixes tag as suggested by David.
* Add David's and Rae's Reviewed-by.

Changes since v1:
* Add Kees's Reviewed-by.
---
 lib/kunit/try-catch.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
index a5cb2ef70a25..73f5007f20ea 100644
--- a/lib/kunit/try-catch.c
+++ b/lib/kunit/try-catch.c
@@ -11,6 +11,7 @@
 #include <linux/completion.h>
 #include <linux/kernel.h>
 #include <linux/kthread.h>
+#include <linux/sched/task.h>
 
 #include "try-catch-impl.h"
 
@@ -65,14 +66,15 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
 	try_catch->context = context;
 	try_catch->try_completion = &try_completion;
 	try_catch->try_result = 0;
-	task_struct = kthread_run(kunit_generic_run_threadfn_adapter,
-				  try_catch,
-				  "kunit_try_catch_thread");
+	task_struct = kthread_create(kunit_generic_run_threadfn_adapter,
+				     try_catch, "kunit_try_catch_thread");
 	if (IS_ERR(task_struct)) {
 		try_catch->try_result = PTR_ERR(task_struct);
 		try_catch->catch(try_catch->context);
 		return;
 	}
+	get_task_struct(task_struct);
+	wake_up_process(task_struct);
 
 	time_remaining = wait_for_completion_timeout(&try_completion,
 						     kunit_test_timeout());
@@ -82,6 +84,7 @@ void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
 		kthread_stop(task_struct);
 	}
 
+	put_task_struct(task_struct);
 	exit_code = try_catch->try_result;
 
 	if (!exit_code)
-- 
2.44.0