releases/6.8.12/kunit-fix-kthread-reference.patch

From d4dfc4d2e8887b54de8f3ecdec6ceaf3d96dc2f9 Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Mon, 8 Apr 2024 09:46:20 +0200
Subject: kunit: Fix kthread reference
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From: Mickaël Salaün <mic@digikod.net>

[ Upstream commit f8aa1b98ce40184521ed95ec26cc115a255183b2 ]

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/20240408074625.65017-3-mic@digikod.net
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 f7825991d576a..d9d1df28cc52e 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"
 
@@ -65,13 +66,14 @@ 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->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());
@@ -81,6 +83,7 @@ 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)
-- 
2.43.0