[PATCH v5 14/22] treewide: Drop WARN_ON_FUNCTION_MISMATCH

Sami Tolvanen
2022-09-08T21:55:43Z

CONFIG_CFI_CLANG no longer breaks cross-module function address
equality, which makes WARN_ON_FUNCTION_MISMATCH unnecessary. Remove
the definition and switch back to WARN_ON_ONCE.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
---
include/asm-generic/bug.h | 16 ----------------
kernel/kthread.c | 3 +--
kernel/workqueue.c | 2 +-
3 files changed, 2 insertions(+), 19 deletions(-)

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index ba1f860af38b..4050b191e1a9 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -220,22 +220,6 @@ extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
# define WARN_ON_SMP(x) ({0;})
#endif

-/*
- * WARN_ON_FUNCTION_MISMATCH() warns if a value doesn't match a
- * function address, and can be useful for catching issues with
- * callback functions, for example.
- *
- * With CONFIG_CFI_CLANG, the warning is disabled because the
- * compiler replaces function addresses taken in C code with
- * local jump table addresses, which breaks cross-module function
- * address equality.
- */
-#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_MODULES)
-# define WARN_ON_FUNCTION_MISMATCH(x, fn) ({ 0; })
-#else
-# define WARN_ON_FUNCTION_MISMATCH(x, fn) WARN_ON_ONCE((x) != (fn))
-#endif
-
#endif /* __ASSEMBLY__ */

#endif
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3c677918d8f2..28a6b7ab4a0f 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -1050,8 +1050,7 @@ static void __kthread_queue_delayed_work(struct kthread_worker *worker,
struct timer_list *timer = &dwork->timer;
struct kthread_work *work = &dwork->work;

- WARN_ON_FUNCTION_MISMATCH(timer->function,
- kthread_delayed_work_timer_fn);
+ WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);

/*
* If @delay is 0, queue @dwork->work immediately. This is for
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index aeea9731ef80..16df315d2a3d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1651,7 +1651,7 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
struct work_struct *work = &dwork->work;

WARN_ON_ONCE(!wq);
- WARN_ON_FUNCTION_MISMATCH(timer->function, delayed_work_timer_fn);
+ WARN_ON_ONCE(timer->function != delayed_work_timer_fn);
WARN_ON_ONCE(timer_pending(timer));
WARN_ON_ONCE(!list_empty(&work->entry));

--
2.37.2.789.g6183377224-goog