Re: kernel/trace/ftrace.c:6651:40: sparse: sparse: incorrect type in assignment (different address spaces)

[Leon Hwang <leon.hwang@linux.dev>]

On 11/9/26 07:59, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   50d05c7c76c96b90462f24debacca971d2e86713
> commit: 092f8ec7dbdc71f5bde9bb0f8dead384d2115a44 ftrace: Protect direct_functions in update_ftrace_direct_mod
> date:   5 weeks ago
> config: x86_64-randconfig-122-20260911 (https://download.01.org/0day-ci/archive/20260911/202609110704.Q3M5vCDV-lkp@intel.com/config)
> compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
> sparse: v0.6.5-rc1
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260911/202609110704.Q3M5vCDV-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Fixes: 092f8ec7dbdc ("ftrace: Protect direct_functions in update_ftrace_direct_mod")
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202609110704.Q3M5vCDV-lkp@intel.com/
> 

Hi,

I reproduced the warning with sparse v0.6.5-rc1. The patch below fixes
it locally.

Could you please retest it with the reported config?

Thanks,
Leon

---

From 03079b720a8cba88b3da579acfbcf88d983a838d Mon Sep 17 00:00:00 2001
From: Leon Hwang <leon.hwang@linux.dev>
Date: Fri, 11 Sep 2026 10:43:13 +0800
Subject: [PATCH] ftrace: Use rcu_assign_pointer() for tmp_ops filter hash

tmp_ops.func_hash->filter_hash is annotated __rcu, but
update_ftrace_direct_mod() assigns hash to it directly. Sparse reports an
address-space mismatch.

Use rcu_assign_pointer() for the assignment.

Fixes: 50b35c9e50a8 ("ftrace: Use hash argument for tmp_ops in
update_ftrace_direct_mod")
Reported-by: kernel test robot <lkp@intel.com>
Closes:
https://lore.kernel.org/oe-kbuild-all/202609110704.Q3M5vCDV-lkp@intel.com/
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
 kernel/trace/ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 53d5db60bfa5..673a54fdf392 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6675,7 +6675,7 @@ int update_ftrace_direct_mod(struct ftrace_ops
*ops, struct ftrace_hash *hash, b

        /* Enable the tmp_ops to have the same functions as the hash
object. */
        ftrace_ops_init(&tmp_ops);
-       tmp_ops.func_hash->filter_hash = hash;
+       rcu_assign_pointer(tmp_ops.func_hash->filter_hash, hash);

        err = register_ftrace_function_nolock(&tmp_ops);
        if (err)
--
2.55.0