diff mbox series

[RFC,v2,13/21] treewide: Drop WARN_ON_FUNCTION_MISMATCH

Message ID 20220513202159.1550547-14-samitolvanen@google.com (mailing list archive)
State New, archived
Headers show
Series KCFI support | expand

Commit Message

Sami Tolvanen May 13, 2022, 8:21 p.m. UTC 
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>
---
 include/asm-generic/bug.h | 16 ----------------
 kernel/kthread.c          |  3 +--
 kernel/workqueue.c        |  2 +-
 3 files changed, 2 insertions(+), 19 deletions(-)

Comments

Kees Cook May 14, 2022, 9:54 p.m. UTC | #1 
On Fri, May 13, 2022 at 01:21:51PM -0700, Sami Tolvanen wrote:
> 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>

This one always felt like a trade-off, so I'm happy to see it go. :)

Reviewed-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

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 50265f69a135..dfeb87876b4a 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 0d2514b4ff0d..18c1a1c09684 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));