Re: [PATCH v2 1/1] coresight: syscfg: fix deadlock on device registration failure

[Leo Yan <leo.yan@arm.com>]

On Mon, Sep 14, 2026 at 03:49:00PM +0800, Yingchao Deng wrote:
> cscfg_create_device() calls put_device() on the error path while holding
> cscfg_mutex.  If device_register() fails, put_device() drops the last
> reference and invokes cscfg_dev_release(), which takes cscfg_mutex again,
> deadlocking.
> 
> Module init and exit are serialized by the kernel, so cscfg_mutex is not
> needed to protect the allocation and freeing of cscfg_mgr.  Remove the
> mutex from cscfg_dev_release() and take it only while cscfg_mgr fields
> are being accessed.
> 
> Fixes: 199380decc5f ("coresight: configfs: Fix unload of configurations on module exit")
> Suggested-by: Leo Yan <leo.yan@arm.com>
> Signed-off-by: Yingchao Deng <dengyingchao@kylinsec.com.cn>

For this patch:

Reviewed-by: Leo Yan <leo.yan@arm.com>

Sashiko reported an issue for null pointer dereference if configfs
init fails fails [1]. It is good to fix it using a separate patch:

@@ -1299,8 +1299,10 @@ int __init cscfg_init(void)

        /* initialise configfs subsystem */
        err = cscfg_configfs_init(cscfg_mgr);
-       if (err)
-               goto exit_err;
+       if (err) {
+               device_unregister(cscfg_device());
+               return err;
+       }

        /* preload built-in configurations */
        err = cscfg_preload(THIS_MODULE);

@Yingchao, do you mind to work out a formal patch for this?

Thanks,
Leo

[1] https://sashiko.dev/#/patchset/6CC680FFAC60931F%2B20260914074900.1711-1-dengyingchao%40kylinsec.com.cn