This is a note to let you know that I've just added the patch titled
target: Obtain se_node_acl->acl_kref during get_initiator_node_acl
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
target-obtain-se_node_acl-acl_kref-during-get_initiator_node_acl.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 21aaa23b0ebbd19334fa461370c03cbb076b3295 Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Date: Thu, 7 Jan 2016 22:09:27 -0800
Subject: target: Obtain se_node_acl->acl_kref during get_initiator_node_acl
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
commit 21aaa23b0ebbd19334fa461370c03cbb076b3295 upstream.
This patch addresses a long standing race where obtaining
se_node_acl->acl_kref in __transport_register_session()
happens a bit too late, and leaves open the potential
for core_tpg_del_initiator_node_acl() to hit a NULL
pointer dereference.
Instead, take ->acl_kref in core_tpg_get_initiator_node_acl()
while se_portal_group->acl_node_mutex is held, and move the
final target_put_nacl() from transport_deregister_session()
into transport_free_session() so that fabric driver login
failure handling using the modern method to still work
as expected.
Also, update core_tpg_get_initiator_node_acl() to take
an extra reference for dynamically generated acls for
demo-mode, before returning to fabric caller. Also
update iscsi-target sendtargets special case handling
to use target_tpg_has_node_acl() when checking if
demo_mode_discovery == true during discovery lookup.
Note the existing wait_for_completion(&acl->acl_free_comp)
in core_tpg_del_initiator_node_acl() does not change.
Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxx>
Cc: Andy Grover <agrover@xxxxxxxxxx>
Cc: Mike Christie <michaelc@xxxxxxxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/target/iscsi/iscsi_target.c | 2 -
drivers/target/target_core_tpg.c | 42 ++++++++++++++++++++++++++++++++-
drivers/target/target_core_transport.c | 19 ++++++++++----
include/target/target_core_fabric.h | 2 +
4 files changed, 57 insertions(+), 8 deletions(-)
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -3436,7 +3436,7 @@ iscsit_build_sendtargets_response(struct
if ((tpg->tpg_attrib.generate_node_acls == 0) &&
(tpg->tpg_attrib.demo_mode_discovery == 0) &&
- (!core_tpg_get_initiator_node_acl(&tpg->tpg_se_tpg,
+ (!target_tpg_has_node_acl(&tpg->tpg_se_tpg,
cmd->conn->sess->sess_ops->InitiatorName))) {
continue;
}
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -75,9 +75,21 @@ struct se_node_acl *core_tpg_get_initiat
unsigned char *initiatorname)
{
struct se_node_acl *acl;
-
+ /*
+ * Obtain se_node_acl->acl_kref using fabric driver provided
+ * initiatorname[] during node acl endpoint lookup driven by
+ * new se_session login.
+ *
+ * The reference is held until se_session shutdown -> release
+ * occurs via fabric driver invoked transport_deregister_session()
+ * or transport_free_session() code.
+ */
mutex_lock(&tpg->acl_node_mutex);
acl = __core_tpg_get_initiator_node_acl(tpg, initiatorname);
+ if (acl) {
+ if (!kref_get_unless_zero(&acl->acl_kref))
+ acl = NULL;
+ }
mutex_unlock(&tpg->acl_node_mutex);
return acl;
@@ -232,6 +244,25 @@ static void target_add_node_acl(struct s
acl->initiatorname);
}
+bool target_tpg_has_node_acl(struct se_portal_group *tpg,
+ const char *initiatorname)
+{
+ struct se_node_acl *acl;
+ bool found = false;
+
+ mutex_lock(&tpg->acl_node_mutex);
+ list_for_each_entry(acl, &tpg->acl_node_list, acl_list) {
+ if (!strcmp(acl->initiatorname, initiatorname)) {
+ found = true;
+ break;
+ }
+ }
+ mutex_unlock(&tpg->acl_node_mutex);
+
+ return found;
+}
+EXPORT_SYMBOL(target_tpg_has_node_acl);
+
struct se_node_acl *core_tpg_check_initiator_node_acl(
struct se_portal_group *tpg,
unsigned char *initiatorname)
@@ -248,6 +279,15 @@ struct se_node_acl *core_tpg_check_initi
acl = target_alloc_node_acl(tpg, initiatorname);
if (!acl)
return NULL;
+ /*
+ * When allocating a dynamically generated node_acl, go ahead
+ * and take the extra kref now before returning to the fabric
+ * driver caller.
+ *
+ * Note this reference will be released at session shutdown
+ * time within transport_free_session() code.
+ */
+ kref_get(&acl->acl_kref);
acl->dynamic_node_acl = 1;
/*
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -341,7 +341,6 @@ void __transport_register_session(
&buf[0], PR_REG_ISID_LEN);
se_sess->sess_bin_isid = get_unaligned_be64(&buf[0]);
}
- kref_get(&se_nacl->acl_kref);
spin_lock_irq(&se_nacl->nacl_sess_lock);
/*
@@ -432,6 +431,7 @@ void target_put_nacl(struct se_node_acl
{
kref_put(&nacl->acl_kref, target_complete_nacl);
}
+EXPORT_SYMBOL(target_put_nacl);
void transport_deregister_session_configfs(struct se_session *se_sess)
{
@@ -464,6 +464,15 @@ EXPORT_SYMBOL(transport_deregister_sessi
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) {
+ se_sess->se_node_acl = NULL;
+ target_put_nacl(se_nacl);
+ }
if (se_sess->sess_cmd_map) {
percpu_ida_destroy(&se_sess->sess_tag_pool);
kvfree(se_sess->sess_cmd_map);
@@ -478,7 +487,7 @@ void transport_deregister_session(struct
const struct target_core_fabric_ops *se_tfo;
struct se_node_acl *se_nacl;
unsigned long flags;
- bool comp_nacl = true, drop_nacl = false;
+ bool drop_nacl = false;
if (!se_tpg) {
transport_free_session(se_sess);
@@ -511,18 +520,16 @@ void transport_deregister_session(struct
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);
- comp_nacl = false;
}
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.
+ * removal context from within transport_free_session() code.
*/
- if (se_nacl && comp_nacl)
- target_put_nacl(se_nacl);
transport_free_session(se_sess);
}
--- a/include/target/target_core_fabric.h
+++ b/include/target/target_core_fabric.h
@@ -168,6 +168,8 @@ void core_allocate_nexus_loss_ua(struct
struct se_node_acl *core_tpg_get_initiator_node_acl(struct se_portal_group *tpg,
unsigned char *);
+bool target_tpg_has_node_acl(struct se_portal_group *tpg,
+ const char *);
struct se_node_acl *core_tpg_check_initiator_node_acl(struct se_portal_group *,
unsigned char *);
int core_tpg_set_initiator_node_queue_depth(struct se_portal_group *,
Patches currently in stable-queue which might be from nab@xxxxxxxxxxxxxxx are
queue-4.4/target-fix-multi-session-dynamic-se_node_acl-double-free-oops.patch
queue-4.4/target-obtain-se_node_acl-acl_kref-during-get_initiator_node_acl.patch