Re: [PATCH] coresight: syscfg: Fix null pointer dereference when configfs init fails

[Mike Leach <mike.leach@arm.com>]

Reviewed-by: Mike Leach <mike.leach@arm.com>

On 9/28/26 13:35, Yingchao Deng wrote:
> If cscfg_configfs_init() fails, cscfg_init() takes the exit_err path:
> 
> 	cscfg_init() -> cscfg_clear_device() -> cscfg_configfs_release()
> 		     -> configfs_unregister_subsystem()
> 
> which tears down a configfs subsystem that was never registered.
> configfs_unregister_subsystem() begins with:
> 
> 	struct dentry *dentry = dget(group->cg_item.ci_dentry);
> 	struct dentry *root = dentry->d_sb->s_root;
> 
> ci_dentry is assigned in configfs_create_dir() only once the subsystem
> directory has been created, which never happened here.  cscfg_mgr
> comes from kzalloc_obj(), so ci_dentry is still NULL, and dget()
> hands a NULL dentry back unchanged - the next line dereferences it.
> 
> Handle the failure in cscfg_init() directly: unregister the device and
> return the error, releasing the devres-allocated config item type and
> cscfg_mgr without touching the subsystem.
> 
> Fixes: a13d5a246aca ("coresight: syscfg: Add initial configfs support")
> Suggested-by: Leo Yan <leo.yan@arm.com>
> Link: https://lore.kernel.org/all/20260924162404.GN200420@e132581.arm.com/
> Signed-off-by: Yingchao Deng <dengyingchao@kylinsec.com.cn>
> ---
>   drivers/hwtracing/coresight/coresight-syscfg.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> index 2bfdd7b45e49..00b29d1656c0 100644
> --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> @@ -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);