[3.5.y.z extended stable] Patch "target/iscsi: Fix network portal creation race" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    target/iscsi: Fix network portal creation race

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From c97dbc7f913dd5599a2cfbfa42ef2cd93aa68c15 Mon Sep 17 00:00:00 2001
From: Andy Grover <agrover at redhat.com>
Date: Fri, 24 Jan 2014 16:18:54 -0800
Subject: target/iscsi: Fix network portal creation race

commit ee291e63293146db64668e8d65eb35c97e8324f4 upstream.

When creating network portals rapidly, such as when restoring a
configuration, LIO's code to reuse existing portals can return a false
negative if the thread hasn't run yet and set np_thread_state to
ISCSI_NP_THREAD_ACTIVE. This causes an error in the network stack
when attempting to bind to the same address/port.

This patch sets NP_THREAD_ACTIVE before the np is placed on g_np_list,
so even if the thread hasn't run yet, iscsit_get_np will return the
existing np.

Also, convert np_lock -> np_mutex + hold across adding new net portal
to g_np_list to prevent a race where two threads may attempt to create
the same network portal, resulting in one of them failing.

(nab: Add missing mutex_unlocks in iscsit_add_np failure paths)
(DanC: Fix incorrect spin_unlock -> spin_unlock_bh)

Signed-off-by: Andy Grover <agrover at redhat.com>
Signed-off-by: Nicholas Bellinger <nab at linux-iscsi.org>
[ luis: backported to 3.5: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/target/iscsi/iscsi_target.c | 34 +++++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 955392e..6e270f9 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -52,7 +52,7 @@
 static LIST_HEAD(g_tiqn_list);
 static LIST_HEAD(g_np_list);
 static DEFINE_SPINLOCK(tiqn_lock);
-static DEFINE_SPINLOCK(np_lock);
+static DEFINE_MUTEX(np_lock);

 static struct idr tiqn_idr;
 struct idr sess_idr;
@@ -264,6 +264,9 @@ int iscsit_deaccess_np(struct iscsi_np *np, struct iscsi_portal_group *tpg)
 	return 0;
 }

+/*
+ * Called with mutex np_lock held
+ */
 static struct iscsi_np *iscsit_get_np(
 	struct __kernel_sockaddr_storage *sockaddr,
 	int network_transport)
@@ -274,11 +277,10 @@ static struct iscsi_np *iscsit_get_np(
 	int ip_match = 0;
 	u16 port;

-	spin_lock_bh(&np_lock);
 	list_for_each_entry(np, &g_np_list, np_list) {
-		spin_lock(&np->np_thread_lock);
+		spin_lock_bh(&np->np_thread_lock);
 		if (np->np_thread_state != ISCSI_NP_THREAD_ACTIVE) {
-			spin_unlock(&np->np_thread_lock);
+			spin_unlock_bh(&np->np_thread_lock);
 			continue;
 		}

@@ -311,13 +313,11 @@ static struct iscsi_np *iscsit_get_np(
 			 * while iscsi_tpg_add_network_portal() is called.
 			 */
 			np->np_exports++;
-			spin_unlock(&np->np_thread_lock);
-			spin_unlock_bh(&np_lock);
+			spin_unlock_bh(&np->np_thread_lock);
 			return np;
 		}
-		spin_unlock(&np->np_thread_lock);
+		spin_unlock_bh(&np->np_thread_lock);
 	}
-	spin_unlock_bh(&np_lock);

 	return NULL;
 }
@@ -331,16 +331,22 @@ struct iscsi_np *iscsit_add_np(
 	struct sockaddr_in6 *sock_in6;
 	struct iscsi_np *np;
 	int ret;
+
+	mutex_lock(&np_lock);
+
 	/*
 	 * Locate the existing struct iscsi_np if already active..
 	 */
 	np = iscsit_get_np(sockaddr, network_transport);
-	if (np)
+	if (np) {
+		mutex_unlock(&np_lock);
 		return np;
+	}

 	np = kzalloc(sizeof(struct iscsi_np), GFP_KERNEL);
 	if (!np) {
 		pr_err("Unable to allocate memory for struct iscsi_np\n");
+		mutex_unlock(&np_lock);
 		return ERR_PTR(-ENOMEM);
 	}

@@ -363,6 +369,7 @@ struct iscsi_np *iscsit_add_np(
 	ret = iscsi_target_setup_login_socket(np, sockaddr);
 	if (ret != 0) {
 		kfree(np);
+		mutex_unlock(&np_lock);
 		return ERR_PTR(ret);
 	}

@@ -371,6 +378,7 @@ struct iscsi_np *iscsit_add_np(
 		pr_err("Unable to create kthread: iscsi_np\n");
 		ret = PTR_ERR(np->np_thread);
 		kfree(np);
+		mutex_unlock(&np_lock);
 		return ERR_PTR(ret);
 	}
 	/*
@@ -381,10 +389,10 @@ struct iscsi_np *iscsit_add_np(
 	 * point because iscsi_np has not been added to g_np_list yet.
 	 */
 	np->np_exports = 1;
+	np->np_thread_state = ISCSI_NP_THREAD_ACTIVE;

-	spin_lock_bh(&np_lock);
 	list_add_tail(&np->np_list, &g_np_list);
-	spin_unlock_bh(&np_lock);
+	mutex_unlock(&np_lock);

 	pr_debug("CORE[0] - Added Network Portal: %s:%hu on %s\n",
 		np->np_ip, np->np_port, (np->np_network_transport == ISCSI_TCP) ?
@@ -455,9 +463,9 @@ int iscsit_del_np(struct iscsi_np *np)
 	}
 	iscsit_del_np_comm(np);

-	spin_lock_bh(&np_lock);
+	mutex_lock(&np_lock);
 	list_del(&np->np_list);
-	spin_unlock_bh(&np_lock);
+	mutex_unlock(&np_lock);

 	pr_debug("CORE[0] - Removed Network Portal: %s:%hu on %s\n",
 		np->np_ip, np->np_port, (np->np_network_transport == ISCSI_TCP) ?
--
1.8.3.2