IB: refcount race fixes

Fix race condition during destruction calls to avoid possibility of
accessing object after it has been freed.  Instead of waking up a wait
queue directly, which is susceptible to a race where the object is
freed between the reference count going to 0 and the wake_up(), use a
completion to wait in the function doing the freeing.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

5 files changed, 52 insertions, 44 deletions

diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
index 7cfedb8d9bcd..86fee43502cd 100644
--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -34,6 +34,8 @@
  *
  * $Id: cm.c 2821 2005-07-08 17:07:28Z sean.hefty $
  */
+
+#include <linux/completion.h>
 #include <linux/dma-mapping.h>
 #include <linux/err.h>
 #include <linux/idr.h>
@@ -122,7 +124,7 @@ struct cm_id_private {
         struct rb_node service_node;
         struct rb_node sidr_id_node;
         spinlock_t lock;        /* Do not acquire inside cm.lock */
-        wait_queue_head_t wait;
+        struct completion comp;
         atomic_t refcount;
 
         struct ib_mad_send_buf *msg;
@@ -159,7 +161,7 @@ static void cm_work_handler(void *data);
 static inline void cm_deref_id(struct cm_id_private *cm_id_priv)
 {
         if (atomic_dec_and_test(&cm_id_priv->refcount))
-                wake_up(&cm_id_priv->wait);
+                complete(&cm_id_priv->comp);
 }
 
 static int cm_alloc_msg(struct cm_id_private *cm_id_priv,
@@ -559,7 +561,7 @@ struct ib_cm_id *ib_create_cm_id(struct ib_device *device,
                 goto error;
 
         spin_lock_init(&cm_id_priv->lock);
-        init_waitqueue_head(&cm_id_priv->wait);
+        init_completion(&cm_id_priv->comp);
         INIT_LIST_HEAD(&cm_id_priv->work_list);
         atomic_set(&cm_id_priv->work_count, -1);
         atomic_set(&cm_id_priv->refcount, 1);
@@ -724,8 +726,8 @@ retest:
         }
 
         cm_free_id(cm_id->local_id);
-        atomic_dec(&cm_id_priv->refcount);
-        wait_event(cm_id_priv->wait, !atomic_read(&cm_id_priv->refcount));
+        cm_deref_id(cm_id_priv);
+        wait_for_completion(&cm_id_priv->comp);
         while ((work = cm_dequeue_work(cm_id_priv)) != NULL)
                 cm_free_work(work);
         if (cm_id_priv->private_data && cm_id_priv->private_data_len)
diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c
index 469b6923a2e2..5ad41a64314c 100644
--- a/drivers/infiniband/core/mad.c
+++ b/drivers/infiniband/core/mad.c
@@ -352,7 +352,7 @@ struct ib_mad_agent *ib_register_mad_agent(struct ib_device *device,
         INIT_WORK(&mad_agent_priv->local_work, local_completions,
                    mad_agent_priv);
         atomic_set(&mad_agent_priv->refcount, 1);
-        init_waitqueue_head(&mad_agent_priv->wait);
+        init_completion(&mad_agent_priv->comp);
 
         return &mad_agent_priv->agent;
 
@@ -467,7 +467,7 @@ struct ib_mad_agent *ib_register_mad_snoop(struct ib_device *device,
         mad_snoop_priv->agent.qp = port_priv->qp_info[qpn].qp;
         mad_snoop_priv->agent.port_num = port_num;
         mad_snoop_priv->mad_snoop_flags = mad_snoop_flags;
-        init_waitqueue_head(&mad_snoop_priv->wait);
+        init_completion(&mad_snoop_priv->comp);
         mad_snoop_priv->snoop_index = register_snoop_agent(
                                                 &port_priv->qp_info[qpn],
                                                 mad_snoop_priv);
@@ -486,6 +486,18 @@ error1:
 }
 EXPORT_SYMBOL(ib_register_mad_snoop);
 
+static inline void deref_mad_agent(struct ib_mad_agent_private *mad_agent_priv)
+{
+        if (atomic_dec_and_test(&mad_agent_priv->refcount))
+                complete(&mad_agent_priv->comp);
+}
+
+static inline void deref_snoop_agent(struct ib_mad_snoop_private *mad_snoop_priv)
+{
+        if (atomic_dec_and_test(&mad_snoop_priv->refcount))
+                complete(&mad_snoop_priv->comp);
+}
+
 static void unregister_mad_agent(struct ib_mad_agent_private *mad_agent_priv)
 {
         struct ib_mad_port_private *port_priv;
@@ -509,9 +521,8 @@ static void unregister_mad_agent(struct ib_mad_agent_private *mad_agent_priv)
         flush_workqueue(port_priv->wq);
         ib_cancel_rmpp_recvs(mad_agent_priv);
 
-        atomic_dec(&mad_agent_priv->refcount);
-        wait_event(mad_agent_priv->wait,
-                   !atomic_read(&mad_agent_priv->refcount));
+        deref_mad_agent(mad_agent_priv);
+        wait_for_completion(&mad_agent_priv->comp);
 
         kfree(mad_agent_priv->reg_req);
         ib_dereg_mr(mad_agent_priv->agent.mr);
@@ -529,9 +540,8 @@ static void unregister_mad_snoop(struct ib_mad_snoop_private *mad_snoop_priv)
         atomic_dec(&qp_info->snoop_count);
         spin_unlock_irqrestore(&qp_info->snoop_lock, flags);
 
-        atomic_dec(&mad_snoop_priv->refcount);
-        wait_event(mad_snoop_priv->wait,
-                   !atomic_read(&mad_snoop_priv->refcount));
+        deref_snoop_agent(mad_snoop_priv);
+        wait_for_completion(&mad_snoop_priv->comp);
 
         kfree(mad_snoop_priv);
 }
@@ -600,8 +610,7 @@ static void snoop_send(struct ib_mad_qp_info *qp_info,
                 spin_unlock_irqrestore(&qp_info->snoop_lock, flags);
                 mad_snoop_priv->agent.snoop_handler(&mad_snoop_priv->agent,
                                                     send_buf, mad_send_wc);
-                if (atomic_dec_and_test(&mad_snoop_priv->refcount))
-                        wake_up(&mad_snoop_priv->wait);
+                deref_snoop_agent(mad_snoop_priv);
                 spin_lock_irqsave(&qp_info->snoop_lock, flags);
         }
         spin_unlock_irqrestore(&qp_info->snoop_lock, flags);
@@ -626,8 +635,7 @@ static void snoop_recv(struct ib_mad_qp_info *qp_info,
                 spin_unlock_irqrestore(&qp_info->snoop_lock, flags);
                 mad_snoop_priv->agent.recv_handler(&mad_snoop_priv->agent,
                                                    mad_recv_wc);
-                if (atomic_dec_and_test(&mad_snoop_priv->refcount))
-                        wake_up(&mad_snoop_priv->wait);
+                deref_snoop_agent(mad_snoop_priv);
                 spin_lock_irqsave(&qp_info->snoop_lock, flags);
         }
         spin_unlock_irqrestore(&qp_info->snoop_lock, flags);
@@ -968,8 +976,7 @@ void ib_free_send_mad(struct ib_mad_send_buf *send_buf)
 
         free_send_rmpp_list(mad_send_wr);
         kfree(send_buf->mad);
-        if (atomic_dec_and_test(&mad_agent_priv->refcount))
-                wake_up(&mad_agent_priv->wait);
+        deref_mad_agent(mad_agent_priv);
 }
 EXPORT_SYMBOL(ib_free_send_mad);
 
@@ -1757,8 +1764,7 @@ static void ib_mad_complete_recv(struct ib_mad_agent_private *mad_agent_priv,
                 mad_recv_wc = ib_process_rmpp_recv_wc(mad_agent_priv,
                                                       mad_recv_wc);
                 if (!mad_recv_wc) {
-                        if (atomic_dec_and_test(&mad_agent_priv->refcount))
-                                wake_up(&mad_agent_priv->wait);
+                        deref_mad_agent(mad_agent_priv);
                         return;
                 }
         }
@@ -1770,8 +1776,7 @@ static void ib_mad_complete_recv(struct ib_mad_agent_private *mad_agent_priv,
                 if (!mad_send_wr) {
                         spin_unlock_irqrestore(&mad_agent_priv->lock, flags);
                         ib_free_recv_mad(mad_recv_wc);
-                        if (atomic_dec_and_test(&mad_agent_priv->refcount))
-                                wake_up(&mad_agent_priv->wait);
+                        deref_mad_agent(mad_agent_priv);
                         return;
                 }
                 ib_mark_mad_done(mad_send_wr);
@@ -1790,8 +1795,7 @@ static void ib_mad_complete_recv(struct ib_mad_agent_private *mad_agent_priv,
         } else {
                 mad_agent_priv->agent.recv_handler(&mad_agent_priv->agent,
                                                    mad_recv_wc);
-                if (atomic_dec_and_test(&mad_agent_priv->refcount))
-                        wake_up(&mad_agent_priv->wait);
+                deref_mad_agent(mad_agent_priv);
         }
 }
 
@@ -2021,8 +2025,7 @@ void ib_mad_complete_send_wr(struct ib_mad_send_wr_private *mad_send_wr,
                                                    mad_send_wc);
 
         /* Release reference on agent taken when sending */
-        if (atomic_dec_and_test(&mad_agent_priv->refcount))
-                wake_up(&mad_agent_priv->wait);
+        deref_mad_agent(mad_agent_priv);
         return;
 done:
         spin_unlock_irqrestore(&mad_agent_priv->lock, flags);
diff --git a/drivers/infiniband/core/mad_priv.h b/drivers/infiniband/core/mad_priv.h
index 6c9c133d71ef..b4fa28d3160f 100644
--- a/drivers/infiniband/core/mad_priv.h
+++ b/drivers/infiniband/core/mad_priv.h
@@ -37,6 +37,7 @@
 #ifndef __IB_MAD_PRIV_H__
 #define __IB_MAD_PRIV_H__
 
+#include <linux/completion.h>
 #include <linux/pci.h>
 #include <linux/kthread.h>
 #include <linux/workqueue.h>
@@ -108,7 +109,7 @@ struct ib_mad_agent_private {
         struct list_head rmpp_list;
 
         atomic_t refcount;
-        wait_queue_head_t wait;
+        struct completion comp;
 };
 
 struct ib_mad_snoop_private {
@@ -117,7 +118,7 @@ struct ib_mad_snoop_private {
         int snoop_index;
         int mad_snoop_flags;
         atomic_t refcount;
-        wait_queue_head_t wait;
+        struct completion comp;
 };
 
 struct ib_mad_send_wr_private {
diff --git a/drivers/infiniband/core/mad_rmpp.c b/drivers/infiniband/core/mad_rmpp.c
index dfd4e588ce03..d4704e054e30 100644
--- a/drivers/infiniband/core/mad_rmpp.c
+++ b/drivers/infiniband/core/mad_rmpp.c
@@ -49,7 +49,7 @@ struct mad_rmpp_recv {
         struct list_head list;
         struct work_struct timeout_work;
         struct work_struct cleanup_work;
-        wait_queue_head_t wait;
+        struct completion comp;
         enum rmpp_state state;
         spinlock_t lock;
         atomic_t refcount;
@@ -69,10 +69,16 @@ struct mad_rmpp_recv {
         u8 method;
 };
 
+static inline void deref_rmpp_recv(struct mad_rmpp_recv *rmpp_recv)
+{
+        if (atomic_dec_and_test(&rmpp_recv->refcount))
+                complete(&rmpp_recv->comp);
+}
+
 static void destroy_rmpp_recv(struct mad_rmpp_recv *rmpp_recv)
 {
-        atomic_dec(&rmpp_recv->refcount);
-        wait_event(rmpp_recv->wait, !atomic_read(&rmpp_recv->refcount));
+        deref_rmpp_recv(rmpp_recv);
+        wait_for_completion(&rmpp_recv->comp);
         ib_destroy_ah(rmpp_recv->ah);
         kfree(rmpp_recv);
 }
@@ -253,7 +259,7 @@ create_rmpp_recv(struct ib_mad_agent_private *agent,
                 goto error;
 
         rmpp_recv->agent = agent;
-        init_waitqueue_head(&rmpp_recv->wait);
+        init_completion(&rmpp_recv->comp);
         INIT_WORK(&rmpp_recv->timeout_work, recv_timeout_handler, rmpp_recv);
         INIT_WORK(&rmpp_recv->cleanup_work, recv_cleanup_handler, rmpp_recv);
         spin_lock_init(&rmpp_recv->lock);
@@ -279,12 +285,6 @@ error:	kfree(rmpp_recv);
         return NULL;
 }
 
-static inline void deref_rmpp_recv(struct mad_rmpp_recv *rmpp_recv)
-{
-        if (atomic_dec_and_test(&rmpp_recv->refcount))
-                wake_up(&rmpp_recv->wait);
-}
-
 static struct mad_rmpp_recv *
 find_rmpp_recv(struct ib_mad_agent_private *agent,
                struct ib_mad_recv_wc *mad_recv_wc)
diff --git a/drivers/infiniband/core/ucm.c b/drivers/infiniband/core/ucm.c
index f6a05965a4e8..9164a09b6ccd 100644
--- a/drivers/infiniband/core/ucm.c
+++ b/drivers/infiniband/core/ucm.c
@@ -32,6 +32,8 @@
  *
  * $Id: ucm.c 2594 2005-06-13 19:46:02Z libor $
  */
+
+#include <linux/completion.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/module.h>
@@ -72,7 +74,7 @@ struct ib_ucm_file {
 
 struct ib_ucm_context {
         int                 id;
-        wait_queue_head_t   wait;
+        struct completion   comp;
         atomic_t            ref;
         int                 events_reported;
 
@@ -138,7 +140,7 @@ static struct ib_ucm_context *ib_ucm_ctx_get(struct ib_ucm_file *file, int id)
 static void ib_ucm_ctx_put(struct ib_ucm_context *ctx)
 {
         if (atomic_dec_and_test(&ctx->ref))
-                wake_up(&ctx->wait);
+                complete(&ctx->comp);
 }
 
 static inline int ib_ucm_new_cm_id(int event)
@@ -178,7 +180,7 @@ static struct ib_ucm_context *ib_ucm_ctx_alloc(struct ib_ucm_file *file)
                 return NULL;
 
         atomic_set(&ctx->ref, 1);
-        init_waitqueue_head(&ctx->wait);
+        init_completion(&ctx->comp);
         ctx->file = file;
         INIT_LIST_HEAD(&ctx->events);
 
@@ -586,8 +588,8 @@ static ssize_t ib_ucm_destroy_id(struct ib_ucm_file *file,
         if (IS_ERR(ctx))
                 return PTR_ERR(ctx);
 
-        atomic_dec(&ctx->ref);
-        wait_event(ctx->wait, !atomic_read(&ctx->ref));
+        ib_ucm_ctx_put(ctx);
+        wait_for_completion(&ctx->comp);
 
         /* No new events will be generated after destroying the cm_id. */
         ib_destroy_cm_id(ctx->cm_id);