diff mbox series

[2/2] target: core: de-RCU of se_lun and se_lun acl

Message ID 20220720112852.11440-3-d.bogdanov@yadro.com
State Superseded
Headers show
Series target: core: fix race during ACL removal | expand

Commit Message

Dmitry Bogdanov July 20, 2022, 11:28 a.m. UTC 
se_lun and se_lun_acl are immutable pointers of struct se_dev_entry.
Remove RCU usage for access to those pointers.

Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
---
 drivers/target/target_core_alua.c   |  3 +--
 drivers/target/target_core_device.c | 29 +++++++++++-----------------
 drivers/target/target_core_pr.c     | 30 +++++++++--------------------
 drivers/target/target_core_stat.c   | 10 ++++------
 drivers/target/target_core_xcopy.c  |  2 +-
 include/target/target_core_base.h   |  4 ++--
 6 files changed, 28 insertions(+), 50 deletions(-)

Comments

Mike Christie July 26, 2022, 10:38 p.m. UTC | #1 
On 7/20/22 6:28 AM, Dmitry Bogdanov wrote:
> @@ -1437,34 +1435,26 @@ static void core_scsi3_nodeacl_undepend_item(struct se_node_acl *nacl)
>  
>  static int core_scsi3_lunacl_depend_item(struct se_dev_entry *se_deve)
>  {
> -	struct se_lun_acl *lun_acl;
> -
>  	/*
>  	 * For nacl->dynamic_node_acl=1
>  	 */
> -	lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
> -				kref_read(&se_deve->pr_kref) != 0);
> -	if (!lun_acl)
> +	if (!se_deve->se_lun_acl)
>  		return 0;

Will se_lun_acl and se_lun ever be NULL now? Should this maybe be a
WARN_ON or return a -EXYZ error code like when target_depend_item fails
at the bottom of the function?


I don't think it's a problem with your patch. I think we had issues
before it. If they were NULL then I think we can hit issues like:

1. __core_scsi3_alloc_registration calls core_scsi3_lunacl_depend_item.
If se_lun_acl is NULL and we return 0.

2. __core_scsi3_alloc_registration and other callers treat 0 as success.

3. It then does:

dest_lun = deve_tmp->se_lun;

pr_reg_atp = __core_scsi3_do_alloc_registration(dev,
 				nacl_tmp, dest_lun, deve_tmp,

4. So if se_lun is also NULL then for __core_scsi3_do_alloc_registration's
args we have:

dest_deve, as non-NULL
lun as NULL

5. __core_scsi3_do_alloc_registration will then do a

        pr_reg->pr_aptpl_target_lun = lun->unpacked_lun;
        pr_reg->tg_pt_sep_rtpi = lun->lun_rtpi;

and since lun is NULL we will crash.




>  
> -	return target_depend_item(&lun_acl->se_lun_group.cg_item);
> +	return target_depend_item(&se_deve->se_lun_acl->se_lun_group.cg_item);
>  }
>  
>  static void core_scsi3_lunacl_undepend_item(struct se_dev_entry *se_deve)
>  {
> -	struct se_lun_acl *lun_acl;
> -
> -	/*
> +/*

Just drop the misformatting bit above.

>  	 * For nacl->dynamic_node_acl=1
>  	 */
> -	lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
> -				kref_read(&se_deve->pr_kref) != 0);
> -	if (!lun_acl) {
> +	if (!se_deve->se_lun_acl) {
>  		kref_put(&se_deve->pr_kref, target_pr_kref_release);
>  		return;
>  	}
>  
> -	target_undepend_item(&lun_acl->se_lun_group.cg_item);
> +	target_undepend_item(&se_deve->se_lun_acl->se_lun_group.cg_item);
>  	kref_put(&se_deve->pr_kref, target_pr_kref_release);
>  }
Dmitry Bogdanov July 27, 2022, 7:36 a.m. UTC | #2 
On Tue, Jul 26, 2022 at 05:38:52PM -0500, Mike Christie wrote:
> 
> On 7/20/22 6:28 AM, Dmitry Bogdanov wrote:
> > @@ -1437,34 +1435,26 @@ static void core_scsi3_nodeacl_undepend_item(struct se_node_acl *nacl)
> >
> >  static int core_scsi3_lunacl_depend_item(struct se_dev_entry *se_deve)
> >  {
> > -     struct se_lun_acl *lun_acl;
> > -
> >       /*
> >        * For nacl->dynamic_node_acl=1
> >        */
> > -     lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
> > -                             kref_read(&se_deve->pr_kref) != 0);
> > -     if (!lun_acl)
> > +     if (!se_deve->se_lun_acl)
> >               return 0;
> 
> Will se_lun_acl and se_lun ever be NULL now? Should this maybe be a
> WARN_ON or return a -EXYZ error code like when target_depend_item fails
> at the bottom of the function?
After the first patch from the patchset deve->se_lun_acl is always NULL
for deve on a dynamyc ACL, and always NOT NULL for deve on a configured
ACL, and deve->se_lun is never NULL.

> 
> I don't think it's a problem with your patch. I think we had issues
> before it. If they were NULL then I think we can hit issues like:
> 
> 1. __core_scsi3_alloc_registration calls core_scsi3_lunacl_depend_item.
> If se_lun_acl is NULL and we return 0.
> 
> 2. __core_scsi3_alloc_registration and other callers treat 0 as success.
> 
> 3. It then does:
> 
> dest_lun = deve_tmp->se_lun;
> 
> pr_reg_atp = __core_scsi3_do_alloc_registration(dev,
>                                 nacl_tmp, dest_lun, deve_tmp,
>  
> 4. So if se_lun is also NULL then for __core_scsi3_do_alloc_registration's
> args we have:
> 
> dest_deve, as non-NULL
> lun as NULL
> 
> 5. __core_scsi3_do_alloc_registration will then do a
> 
>         pr_reg->pr_aptpl_target_lun = lun->unpacked_lun;
>         pr_reg->tg_pt_sep_rtpi = lun->lun_rtpi;
> 
> and since lun is NULL we will crash.

I think it was not possible even before my patches becasue deve->se_lun
NULLing was after waiting for deve->pr_kref == 0, which is incremented
in PR OUT handling under spinlock for lun->lun_deve_list. There
everything is safe.

> 
> 
> 
> >
> > -     return target_depend_item(&lun_acl->se_lun_group.cg_item);
> > +     return target_depend_item(&se_deve->se_lun_acl->se_lun_group.cg_item);
> >  }
> >
> >  static void core_scsi3_lunacl_undepend_item(struct se_dev_entry *se_deve)
> >  {
> > -     struct se_lun_acl *lun_acl;
> > -
> > -     /*
> > +/*
> 
> Just drop the misformatting bit above.
oops, will drop it.

> >        * For nacl->dynamic_node_acl=1
> >        */
> > -     lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
> > -                             kref_read(&se_deve->pr_kref) != 0);
> > -     if (!lun_acl) {
> > +     if (!se_deve->se_lun_acl) {
> >               kref_put(&se_deve->pr_kref, target_pr_kref_release);
> >               return;
> >       }
> >
> > -     target_undepend_item(&lun_acl->se_lun_group.cg_item);
> > +     target_undepend_item(&se_deve->se_lun_acl->se_lun_group.cg_item);
> >       kref_put(&se_deve->pr_kref, target_pr_kref_release);
> >  }
diff mbox series

Patch

diff --git a/drivers/target/target_core_alua.c b/drivers/target/target_core_alua.c
index 58df0145e8d0..fb91423a4e2e 100644
--- a/drivers/target/target_core_alua.c
+++ b/drivers/target/target_core_alua.c
@@ -934,8 +934,7 @@  static void core_alua_queue_state_change_ua(struct t10_alua_tg_pt_gp *tg_pt_gp)
 
 		spin_lock(&lun->lun_deve_lock);
 		list_for_each_entry(se_deve, &lun->lun_deve_list, lun_link) {
-			lacl = rcu_dereference_check(se_deve->se_lun_acl,
-					lockdep_is_held(&lun->lun_deve_lock));
+			lacl = se_deve->se_lun_acl;
 
 			/*
 			 * spc4r37 p.242:
diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 335f8cbfe633..01b804789e0b 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -75,7 +75,7 @@  transport_lookup_cmd_lun(struct se_cmd *se_cmd)
 			return TCM_WRITE_PROTECTED;
 		}
 
-		se_lun = rcu_dereference(deve->se_lun);
+		se_lun = deve->se_lun;
 
 		if (!percpu_ref_tryget_live(&se_lun->lun_ref)) {
 			se_lun = NULL;
@@ -152,7 +152,7 @@  int transport_lookup_tmr_lun(struct se_cmd *se_cmd)
 	rcu_read_lock();
 	deve = target_nacl_find_deve(nacl, se_cmd->orig_fe_lun);
 	if (deve) {
-		se_lun = rcu_dereference(deve->se_lun);
+		se_lun = deve->se_lun;
 
 		if (!percpu_ref_tryget_live(&se_lun->lun_ref)) {
 			se_lun = NULL;
@@ -216,7 +216,7 @@  struct se_dev_entry *core_get_se_deve_from_rtpi(
 
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
-		lun = rcu_dereference(deve->se_lun);
+		lun = deve->se_lun;
 		if (!lun) {
 			pr_err("%s device entries device pointer is"
 				" NULL, but Initiator has access.\n",
@@ -243,11 +243,8 @@  void core_free_device_list_for_node(
 	struct se_dev_entry *deve;
 
 	mutex_lock(&nacl->lun_entry_mutex);
-	hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
-		struct se_lun *lun = rcu_dereference_check(deve->se_lun,
-					lockdep_is_held(&nacl->lun_entry_mutex));
-		core_disable_device_list_for_node(lun, deve, nacl, tpg);
-	}
+	hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link)
+		core_disable_device_list_for_node(deve->se_lun, deve, nacl, tpg);
 	mutex_unlock(&nacl->lun_entry_mutex);
 }
 
@@ -334,8 +331,7 @@  int core_enable_device_list_for_node(
 	mutex_lock(&nacl->lun_entry_mutex);
 	orig = target_nacl_find_deve(nacl, mapped_lun);
 	if (orig && orig->se_lun) {
-		struct se_lun *orig_lun = rcu_dereference_check(orig->se_lun,
-					lockdep_is_held(&nacl->lun_entry_mutex));
+		struct se_lun *orig_lun = orig->se_lun;
 
 		if (orig_lun != lun) {
 			pr_err("Existing orig->se_lun doesn't match new lun"
@@ -355,8 +351,8 @@  int core_enable_device_list_for_node(
 			return -EINVAL;
 		}
 
-		rcu_assign_pointer(new->se_lun, lun);
-		rcu_assign_pointer(new->se_lun_acl, lun_acl);
+		new->se_lun = lun;
+		new->se_lun_acl = lun_acl;
 		hlist_del_rcu(&orig->link);
 		hlist_add_head_rcu(&new->link, &nacl->lun_entry_hlist);
 		mutex_unlock(&nacl->lun_entry_mutex);
@@ -374,8 +370,8 @@  int core_enable_device_list_for_node(
 		return 0;
 	}
 
-	rcu_assign_pointer(new->se_lun, lun);
-	rcu_assign_pointer(new->se_lun_acl, lun_acl);
+	new->se_lun = lun;
+	new->se_lun_acl = lun_acl;
 	hlist_add_head_rcu(&new->link, &nacl->lun_entry_hlist);
 	mutex_unlock(&nacl->lun_entry_mutex);
 
@@ -454,10 +450,7 @@  void core_clear_lun_from_tpg(struct se_lun *lun, struct se_portal_group *tpg)
 
 		mutex_lock(&nacl->lun_entry_mutex);
 		hlist_for_each_entry_rcu(deve, &nacl->lun_entry_hlist, link) {
-			struct se_lun *tmp_lun = rcu_dereference_check(deve->se_lun,
-					lockdep_is_held(&nacl->lun_entry_mutex));
-
-			if (lun != tmp_lun)
+			if (lun != deve->se_lun)
 				continue;
 
 			core_disable_device_list_for_node(lun, deve, nacl, tpg);
diff --git a/drivers/target/target_core_pr.c b/drivers/target/target_core_pr.c
index 3829b61b56c1..6bdedf34d6c9 100644
--- a/drivers/target/target_core_pr.c
+++ b/drivers/target/target_core_pr.c
@@ -739,8 +739,7 @@  static struct t10_pr_registration *__core_scsi3_alloc_registration(
 			if (!deve_tmp->se_lun_acl)
 				continue;
 
-			lacl_tmp = rcu_dereference_check(deve_tmp->se_lun_acl,
-						lockdep_is_held(&lun_tmp->lun_deve_lock));
+			lacl_tmp = deve_tmp->se_lun_acl;
 			nacl_tmp = lacl_tmp->se_lun_nacl;
 			/*
 			 * Skip the matching struct se_node_acl that is allocated
@@ -784,8 +783,7 @@  static struct t10_pr_registration *__core_scsi3_alloc_registration(
 			 * the original *pr_reg is processed in
 			 * __core_scsi3_add_registration()
 			 */
-			dest_lun = rcu_dereference_check(deve_tmp->se_lun,
-				kref_read(&deve_tmp->pr_kref) != 0);
+			dest_lun = deve_tmp->se_lun;
 
 			pr_reg_atp = __core_scsi3_do_alloc_registration(dev,
 						nacl_tmp, dest_lun, deve_tmp,
@@ -1437,34 +1435,26 @@  static void core_scsi3_nodeacl_undepend_item(struct se_node_acl *nacl)
 
 static int core_scsi3_lunacl_depend_item(struct se_dev_entry *se_deve)
 {
-	struct se_lun_acl *lun_acl;
-
 	/*
 	 * For nacl->dynamic_node_acl=1
 	 */
-	lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
-				kref_read(&se_deve->pr_kref) != 0);
-	if (!lun_acl)
+	if (!se_deve->se_lun_acl)
 		return 0;
 
-	return target_depend_item(&lun_acl->se_lun_group.cg_item);
+	return target_depend_item(&se_deve->se_lun_acl->se_lun_group.cg_item);
 }
 
 static void core_scsi3_lunacl_undepend_item(struct se_dev_entry *se_deve)
 {
-	struct se_lun_acl *lun_acl;
-
-	/*
+/*
 	 * For nacl->dynamic_node_acl=1
 	 */
-	lun_acl = rcu_dereference_check(se_deve->se_lun_acl,
-				kref_read(&se_deve->pr_kref) != 0);
-	if (!lun_acl) {
+	if (!se_deve->se_lun_acl) {
 		kref_put(&se_deve->pr_kref, target_pr_kref_release);
 		return;
 	}
 
-	target_undepend_item(&lun_acl->se_lun_group.cg_item);
+	target_undepend_item(&se_deve->se_lun_acl->se_lun_group.cg_item);
 	kref_put(&se_deve->pr_kref, target_pr_kref_release);
 }
 
@@ -1751,8 +1741,7 @@  core_scsi3_decode_spec_i_port(
 		 * and then call __core_scsi3_add_registration() in the
 		 * 2nd loop which will never fail.
 		 */
-		dest_lun = rcu_dereference_check(dest_se_deve->se_lun,
-				kref_read(&dest_se_deve->pr_kref) != 0);
+		dest_lun = dest_se_deve->se_lun;
 
 		dest_pr_reg = __core_scsi3_alloc_registration(cmd->se_dev,
 					dest_node_acl, dest_lun, dest_se_deve,
@@ -3446,8 +3435,7 @@  core_scsi3_emulate_pro_register_and_move(struct se_cmd *cmd, u64 res_key,
 	dest_pr_reg = __core_scsi3_locate_pr_reg(dev, dest_node_acl,
 					iport_ptr);
 	if (!dest_pr_reg) {
-		struct se_lun *dest_lun = rcu_dereference_check(dest_se_deve->se_lun,
-				kref_read(&dest_se_deve->pr_kref) != 0);
+		struct se_lun *dest_lun = dest_se_deve->se_lun;
 
 		spin_unlock(&dev->dev_reservation_lock);
 		if (core_scsi3_alloc_registration(cmd->se_dev, dest_node_acl,
diff --git a/drivers/target/target_core_stat.c b/drivers/target/target_core_stat.c
index 62d15bcc3d93..f85ee5b0fd80 100644
--- a/drivers/target/target_core_stat.c
+++ b/drivers/target/target_core_stat.c
@@ -877,7 +877,6 @@  static ssize_t target_stat_auth_dev_show(struct config_item *item,
 	struct se_lun_acl *lacl = auth_to_lacl(item);
 	struct se_node_acl *nacl = lacl->se_lun_nacl;
 	struct se_dev_entry *deve;
-	struct se_lun *lun;
 	ssize_t ret;
 
 	rcu_read_lock();
@@ -886,9 +885,9 @@  static ssize_t target_stat_auth_dev_show(struct config_item *item,
 		rcu_read_unlock();
 		return -ENODEV;
 	}
-	lun = rcu_dereference(deve->se_lun);
+
 	/* scsiDeviceIndex */
-	ret = snprintf(page, PAGE_SIZE, "%u\n", lun->lun_index);
+	ret = snprintf(page, PAGE_SIZE, "%u\n", deve->se_lun->lun_index);
 	rcu_read_unlock();
 	return ret;
 }
@@ -1217,7 +1216,6 @@  static ssize_t target_stat_iport_dev_show(struct config_item *item,
 	struct se_lun_acl *lacl = iport_to_lacl(item);
 	struct se_node_acl *nacl = lacl->se_lun_nacl;
 	struct se_dev_entry *deve;
-	struct se_lun *lun;
 	ssize_t ret;
 
 	rcu_read_lock();
@@ -1226,9 +1224,9 @@  static ssize_t target_stat_iport_dev_show(struct config_item *item,
 		rcu_read_unlock();
 		return -ENODEV;
 	}
-	lun = rcu_dereference(deve->se_lun);
+
 	/* scsiDeviceIndex */
-	ret = snprintf(page, PAGE_SIZE, "%u\n", lun->lun_index);
+	ret = snprintf(page, PAGE_SIZE, "%u\n", deve->se_lun->lun_index);
 	rcu_read_unlock();
 	return ret;
 }
diff --git a/drivers/target/target_core_xcopy.c b/drivers/target/target_core_xcopy.c
index 6bb20aa9c5bc..8713cda0c2fb 100644
--- a/drivers/target/target_core_xcopy.c
+++ b/drivers/target/target_core_xcopy.c
@@ -88,7 +88,7 @@  static int target_xcopy_locate_se_dev_e4(struct se_session *sess,
 		struct se_device *this_dev;
 		int rc;
 
-		this_lun = rcu_dereference(deve->se_lun);
+		this_lun = deve->se_lun;
 		this_dev = rcu_dereference_raw(this_lun->lun_se_dev);
 
 		rc = target_xcopy_locate_se_dev_e4_iter(this_dev, dev_wwn);
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index c2b36f7d917d..8c920456edd9 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -665,9 +665,9 @@  struct se_dev_entry {
 	/* Used for PR SPEC_I_PT=1 and REGISTER_AND_MOVE */
 	struct kref		pr_kref;
 	struct completion	pr_comp;
-	struct se_lun_acl __rcu	*se_lun_acl;
+	struct se_lun_acl	*se_lun_acl;
 	spinlock_t		ua_lock;
-	struct se_lun __rcu	*se_lun;
+	struct se_lun		*se_lun;
 #define DEF_PR_REG_ACTIVE		1
 	unsigned long		deve_flags;
 	struct list_head	alua_port_list;