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target: Fix multi-session dynamic se_node_acl double free OOPs

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This patch addresses a long-standing bug with multi-session
(eg: iscsi-target + iser-target) se_node_acl dynamic free
withini transport_deregister_session().

This bug is caused when a storage endpoint is configured with
demo-mode (generate_node_acls = 1 + cache_dynamic_acls = 1)
initiators, and initiator login creates a new dynamic node acl
and attaches two sessions to it.

After that, demo-mode for the storage instance is disabled via
configfs (generate_node_acls = 0 + cache_dynamic_acls = 0) and
the existing dynamic acl is never converted to an explicit ACL.

The end result is dynamic acl resources are released twice when
the sessions are shutdown in transport_deregister_session().

If the storage instance is not changed to disable demo-mode,
or the dynamic acl is converted to an explict ACL, or there
is only a single session associated with the dynamic ACL,
the bug is not triggered.

To address this big, move the release of dynamic se_node_acl
memory into target_complete_nacl() so it's only freed once
when se_node_acl->acl_kref reaches zero.

(Drop unnecessary list_del_init usage - HCH)

Reported-by: Rob Millner <rlm@daterainc.com>
Tested-by: Rob Millner <rlm@daterainc.com>
Cc: Rob Millner <rlm@daterainc.com>
Cc: stable@vger.kernel.org # 4.1+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Nicholas Bellinger 2016-12-07 12:55:54 -08:00
parent c54eeffbe9
commit 01d4d67355
2 changed files with 44 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

69
drivers/target/target_core_transport.c
View File

@ -457,8 +457,20 @@ static void target_complete_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);
if (!nacl->dynamic_stop) {
complete(&nacl->acl_free_comp);
return;
}
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)
@ -499,12 +511,39 @@ 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;
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))
se_nacl->dynamic_stop = true;
spin_unlock_irqrestore(&se_nacl->nacl_sess_lock, flags);
if (se_nacl->dynamic_stop)
list_del(&se_nacl->acl_list);
}
mutex_unlock(&se_tpg->acl_node_mutex);
if (se_nacl->dynamic_stop)
target_put_nacl(se_nacl);
target_put_nacl(se_nacl);
}
if (se_sess->sess_cmd_map) {
@ -518,16 +557,12 @@ 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);
@ -535,33 +570,15 @@ 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.
*
* For dynamic ACL, target_put_nacl() uses target_complete_nacl()
* to release all remaining generate_node_acl=1 created ACL resources.
*/
transport_free_session(se_sess);

1
include/target/target_core_base.h
View File

@ -538,6 +538,7 @@ struct se_node_acl {
char initiatorname[TRANSPORT_IQN_LEN];
/* Used to signal demo mode created ACL, disabled by default */
bool dynamic_node_acl;
bool dynamic_stop;
u32 queue_depth;
u32 acl_index;
enum target_prot_type saved_prot_type;