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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

authored by

Sami Tolvanen and committed by
Kees Cook 0a5b4128 98173112

+2 -1
+2 -1
kernel/kthread.c
··· 963 963 struct timer_list *timer = &dwork->timer; 964 964 struct kthread_work *work = &dwork->work; 965 965 966 - WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn); 966 + WARN_ON_FUNCTION_MISMATCH(timer->function, 967 + kthread_delayed_work_timer_fn); 967 968 968 969 /* 969 970 * If @delay is 0, queue @dwork->work immediately. This is for