kthread: use WARN_ON_FUNCTION_MISMATCH

With CONFIG_CFI_CLANG, a callback function passed to
__kthread_queue_delayed_work from a module points to a jump table
entry defined in the module instead of the one used in the core
kernel, which breaks function address equality in this check:

  WARN_ON_ONCE(timer->function != ktead_delayed_work_timer_fn);

Use WARN_ON_FUNCTION_MISMATCH() instead to disable the warning
when CFI and modules are both enabled.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-7-samitolvanen@google.com

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 1578973..a1972eb 100644 (file)
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -963,7 +963,8 @@ static void __kthread_queue_delayed_work(struct kthread_worker *worker,
        struct timer_list *timer = &dwork->timer;
        struct kthread_work *work = &dwork->work;
 
-       WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);
+       WARN_ON_FUNCTION_MISMATCH(timer->function,
+                                 kthread_delayed_work_timer_fn);
 
        /*
         * If @delay is 0, queue @dwork->work immediately.  This is for