Re: [PATCH 4/5] target: Fix multi-session dynamic se_node_acl double free OOPs

[Nicholas A. Bellinger]

On Tue, 2017-02-07 at 15:12 -0800, Christoph Hellwig wrote:
> And the real patch after compile fixing it is here of course:
> 

Getting rid of the extra se_node_acl->acl_free_comp seems to make sense
here..

The only potential issue is if returning from configfs syscall
rmdir /sys/kernel/config/target/$FABRIC/$WWN/$TPGT/acls/$INITIATOR/
before se_node_acl memory is released has implications when the
underlying ../$WWN/$TPGT/ is removed immediately after.

In any event, I'll verify this patch with the original test case and use
it instead if everything looks OK.

> diff --git a/drivers/target/target_core_internal.h b/drivers/target/target_core_internal.h
> index 9ab7090f7c83..96c38f30069d 100644
> --- a/drivers/target/target_core_internal.h
> +++ b/drivers/target/target_core_internal.h
> @@ -152,6 +152,7 @@ void	target_qf_do_work(struct work_struct *work);
>  bool	target_check_wce(struct se_device *dev);
>  bool	target_check_fua(struct se_device *dev);
>  void	__target_execute_cmd(struct se_cmd *, bool);
> +void	target_put_nacl(struct se_node_acl *);
>  
>  /* target_core_stat.c */
>  void	target_stat_setup_dev_default_groups(struct se_device *);
> diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
> index d99752c6cd60..08738c87e5b0 100644
> --- a/drivers/target/target_core_tpg.c
> +++ b/drivers/target/target_core_tpg.c
> @@ -197,7 +197,6 @@ static struct se_node_acl *target_alloc_node_acl(struct se_portal_group *tpg,
>  	INIT_LIST_HEAD(&acl->acl_sess_list);
>  	INIT_HLIST_HEAD(&acl->lun_entry_hlist);
>  	kref_init(&acl->acl_kref);
> -	init_completion(&acl->acl_free_comp);
>  	spin_lock_init(&acl->nacl_sess_lock);
>  	mutex_init(&acl->lun_entry_mutex);
>  	atomic_set(&acl->acl_pr_ref_count, 0);
> @@ -370,21 +369,6 @@ void core_tpg_del_initiator_node_acl(struct se_node_acl *acl)
>  	target_shutdown_sessions(acl);
>  
>  	target_put_nacl(acl);
> -	/*
> -	 * Wait for last target_put_nacl() to complete in target_complete_nacl()
> -	 * for active fabric session transport_deregister_session() callbacks.
> -	 */
> -	wait_for_completion(&acl->acl_free_comp);
> -
> -	core_tpg_wait_for_nacl_pr_ref(acl);
> -	core_free_device_list_for_node(acl, tpg);
> -
> -	pr_debug("%s_TPG[%hu] - Deleted ACL with TCQ Depth: %d for %s"
> -		" Initiator Node: %s\n", tpg->se_tpg_tfo->get_fabric_name(),
> -		tpg->se_tpg_tfo->tpg_get_tag(tpg), acl->queue_depth,
> -		tpg->se_tpg_tfo->get_fabric_name(), acl->initiatorname);
> -
> -	kfree(acl);
>  }
>  
>  /*	core_tpg_set_initiator_node_queue_depth():
> diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> index 1cadc9eefa21..9ebd86a8ef41 100644
> --- a/drivers/target/target_core_transport.c
> +++ b/drivers/target/target_core_transport.c
> @@ -453,19 +453,25 @@ ssize_t target_show_dynamic_sessions(struct se_portal_group *se_tpg, char *page)
>  }
>  EXPORT_SYMBOL(target_show_dynamic_sessions);
>  
> -static void target_complete_nacl(struct kref *kref)
> +static void target_destroy_nacl(struct kref *kref)
>  {
>  	struct se_node_acl *nacl = container_of(kref,
>  				struct se_node_acl, acl_kref);
> +	struct se_portal_group *se_tpg = nacl->se_tpg;
>  
> -	complete(&nacl->acl_free_comp);
> +	mutex_lock(&se_tpg->acl_node_mutex);
> +	list_del(&nacl->acl_list);
> +	mutex_unlock(&se_tpg->acl_node_mutex);
> +
> +	core_tpg_wait_for_nacl_pr_ref(nacl);
> +	core_free_device_list_for_node(nacl, se_tpg);
> +	kfree(nacl);
>  }
>  
>  void target_put_nacl(struct se_node_acl *nacl)
>  {
> -	kref_put(&nacl->acl_kref, target_complete_nacl);
> +	kref_put(&nacl->acl_kref, target_destroy_nacl);
>  }
> -EXPORT_SYMBOL(target_put_nacl);
>  
>  void transport_deregister_session_configfs(struct se_session *se_sess)
>  {
> @@ -499,12 +505,40 @@ EXPORT_SYMBOL(transport_deregister_session_configfs);
>  void transport_free_session(struct se_session *se_sess)
>  {
>  	struct se_node_acl *se_nacl = se_sess->se_node_acl;
> +
>  	/*
>  	 * Drop the se_node_acl->nacl_kref obtained from within
>  	 * core_tpg_get_initiator_node_acl().
>  	 */
>  	if (se_nacl) {
> +		struct se_portal_group *se_tpg = se_nacl->se_tpg;
> +		const struct target_core_fabric_ops *se_tfo = se_tpg->se_tpg_tfo;
> +		unsigned long flags;
> +		bool stop = false;
> +
>  		se_sess->se_node_acl = NULL;
> +
> +		/*
> +		 * Also determine if we need to drop the extra ->cmd_kref if
> +		 * it had been previously dynamically generated, and
> +		 * the endpoint is not caching dynamic ACLs.
> +		 */
> +		mutex_lock(&se_tpg->acl_node_mutex);
> +		if (se_nacl->dynamic_node_acl &&
> +		    !se_tfo->tpg_check_demo_mode_cache(se_tpg)) {
> +			spin_lock_irqsave(&se_nacl->nacl_sess_lock, flags);
> +			if (list_empty(&se_nacl->acl_sess_list))
> +				stop = true;
> +			spin_unlock_irqrestore(&se_nacl->nacl_sess_lock, flags);
> +
> +			if (stop)
> +				list_del_init(&se_nacl->acl_list);
> +		}
> +		mutex_unlock(&se_tpg->acl_node_mutex);
> +
> +		if (stop)
> +			target_put_nacl(se_nacl);
> +
>  		target_put_nacl(se_nacl);
>  	}
>  	if (se_sess->sess_cmd_map) {
> @@ -518,16 +552,12 @@ EXPORT_SYMBOL(transport_free_session);
>  void transport_deregister_session(struct se_session *se_sess)
>  {
>  	struct se_portal_group *se_tpg = se_sess->se_tpg;
> -	const struct target_core_fabric_ops *se_tfo;
> -	struct se_node_acl *se_nacl;
>  	unsigned long flags;
> -	bool drop_nacl = false;
>  
>  	if (!se_tpg) {
>  		transport_free_session(se_sess);
>  		return;
>  	}
> -	se_tfo = se_tpg->se_tpg_tfo;
>  
>  	spin_lock_irqsave(&se_tpg->session_lock, flags);
>  	list_del(&se_sess->sess_list);
> @@ -535,35 +565,8 @@ void transport_deregister_session(struct se_session *se_sess)
>  	se_sess->fabric_sess_ptr = NULL;
>  	spin_unlock_irqrestore(&se_tpg->session_lock, flags);
>  
> -	/*
> -	 * Determine if we need to do extra work for this initiator node's
> -	 * struct se_node_acl if it had been previously dynamically generated.
> -	 */
> -	se_nacl = se_sess->se_node_acl;
> -
> -	mutex_lock(&se_tpg->acl_node_mutex);
> -	if (se_nacl && se_nacl->dynamic_node_acl) {
> -		if (!se_tfo->tpg_check_demo_mode_cache(se_tpg)) {
> -			list_del(&se_nacl->acl_list);
> -			drop_nacl = true;
> -		}
> -	}
> -	mutex_unlock(&se_tpg->acl_node_mutex);
> -
> -	if (drop_nacl) {
> -		core_tpg_wait_for_nacl_pr_ref(se_nacl);
> -		core_free_device_list_for_node(se_nacl, se_tpg);
> -		se_sess->se_node_acl = NULL;
> -		kfree(se_nacl);
> -	}
>  	pr_debug("TARGET_CORE[%s]: Deregistered fabric_sess\n",
>  		se_tpg->se_tpg_tfo->get_fabric_name());
> -	/*
> -	 * If last kref is dropping now for an explicit NodeACL, awake sleeping
> -	 * ->acl_free_comp caller to wakeup configfs se_node_acl->acl_group
> -	 * removal context from within transport_free_session() code.
> -	 */
> -
>  	transport_free_session(se_sess);
>  }
>  EXPORT_SYMBOL(transport_deregister_session);
> diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
> index 43edf82e54ff..edad452c3c25 100644
> --- a/include/target/target_core_base.h
> +++ b/include/target/target_core_base.h
> @@ -557,7 +557,6 @@ struct se_node_acl {
>  	struct config_group	acl_fabric_stat_group;
>  	struct list_head	acl_list;
>  	struct list_head	acl_sess_list;
> -	struct completion	acl_free_comp;
>  	struct kref		acl_kref;
>  };
>  
> diff --git a/include/target/target_core_fabric.h b/include/target/target_core_fabric.h
> index 358041bad1da..1c417731b63d 100644
> --- a/include/target/target_core_fabric.h
> +++ b/include/target/target_core_fabric.h
> @@ -125,7 +125,6 @@ void	transport_register_session(struct se_portal_group *,
>  		struct se_node_acl *, struct se_session *, void *);
>  ssize_t	target_show_dynamic_sessions(struct se_portal_group *, char *);
>  void	transport_free_session(struct se_session *);
> -void	target_put_nacl(struct se_node_acl *);
>  void	transport_deregister_session_configfs(struct se_session *);
>  void	transport_deregister_session(struct se_session *);
>  
> --
> To unsubscribe from this list: send the line "unsubscribe target-devel" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html