IB/srp: Avoid duplicate connections

The connection uniqueness check is performed before a new connection
is added to the target list. This patch protects both actions by a
mutex such that simultaneous writes from two different threads into the
"add_target" variable do not result in duplicate connections.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Roland Dreier <roland@purestorage.com>

2 files changed, 10 insertions, 3 deletions

diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index 2ec9c05814f6..3294f10316a0 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -2614,6 +2614,8 @@ static ssize_t srp_create_target(struct device *dev,
         target->tl_retry_count  = 7;
         target->queue_size      = SRP_DEFAULT_QUEUE_SIZE;
 
+        mutex_lock(&host->add_target_mutex);
+
         ret = srp_parse_options(buf, target);
         if (ret)
                 goto err;
@@ -2682,7 +2684,11 @@ static ssize_t srp_create_target(struct device *dev,
                      be64_to_cpu(target->service_id),
                      target->path.sgid.raw, target->path.dgid.raw);
 
-        return count;
+        ret = count;
+
+out:
+        mutex_unlock(&host->add_target_mutex);
+        return ret;
 
 err_disconnect:
         srp_disconnect_target(target);
@@ -2698,8 +2704,7 @@ err_free_mem:
 
 err:
         scsi_host_put(target_host);
-
-        return ret;
+        goto out;
 }
 
 static DEVICE_ATTR(add_target, S_IWUSR, NULL, srp_create_target);
@@ -2735,6 +2740,7 @@ static struct srp_host *srp_add_port(struct srp_device *device, u8 port)
         INIT_LIST_HEAD(&host->target_list);
         spin_lock_init(&host->target_lock);
         init_completion(&host->released);
+        mutex_init(&host->add_target_mutex);
         host->srp_dev = device;
         host->port = port;
 
diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
index 575681063f38..aad27b7b4a46 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.h
+++ b/drivers/infiniband/ulp/srp/ib_srp.h
@@ -105,6 +105,7 @@ struct srp_host {
         spinlock_t              target_lock;
         struct completion       released;
         struct list_head        list;
+        struct mutex            add_target_mutex;
 };
 
 struct srp_request {