RDMA/core: Use READ_ONCE for ib_ufile.async_file

The writer for async_file holds the ucontext_lock, while the readers are
left unlocked. Most readers rely on an implicit locking, either by having
a uobject (which cannot be created before a context) or by holding the
ib_ufile kref.

However ib_uverbs_free_hw_resources() has no implicit lock and has a
possible race. Make this all clear and sane by using READ_ONCE
consistently.

Link: https://lore.kernel.org/r/1578504126-9400-15-git-send-email-yishaih@mellanox.com
Signed-off-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index ccde5d2..aaa5c75 100644 (file)
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -220,11 +220,9 @@ void ib_uverbs_init_async_event_file(struct ib_uverbs_async_event_file *ev_file)
 void ib_uverbs_free_event_queue(struct ib_uverbs_event_queue *event_queue);
 void ib_uverbs_flow_resources_free(struct ib_uflow_resources *uflow_res);
 
-void ib_uverbs_release_ucq(struct ib_uverbs_file *file,
-                          struct ib_uverbs_completion_event_file *ev_file,
+void ib_uverbs_release_ucq(struct ib_uverbs_completion_event_file *ev_file,
                           struct ib_ucq_object *uobj);
-void ib_uverbs_release_uevent(struct ib_uverbs_file *file,
-                             struct ib_uevent_object *uobj);
+void ib_uverbs_release_uevent(struct ib_uevent_object *uobj);
 void ib_uverbs_release_file(struct kref *ref);
 
 void ib_uverbs_comp_handler(struct ib_cq *cq, void *cq_context);

diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index ced1384..29b1b5a 100644 (file)
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -1056,7 +1056,7 @@ err_free:
        kfree(cq);
 err_file:
        if (ev_file)
-               ib_uverbs_release_ucq(attrs->ufile, ev_file, obj);
+               ib_uverbs_release_ucq(ev_file, obj);
 
 err:
        uobj_alloc_abort(&obj->uevent.uobject, attrs);

diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 121e65f..1f279b0 100644 (file)
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -125,9 +125,8 @@ static void ib_uverbs_release_dev(struct device *device)
        kfree(dev);
 }
 
-void ib_uverbs_release_ucq(struct ib_uverbs_file *file,
-                         struct ib_uverbs_completion_event_file *ev_file,
-                         struct ib_ucq_object *uobj)
+void ib_uverbs_release_ucq(struct ib_uverbs_completion_event_file *ev_file,
+                          struct ib_ucq_object *uobj)
 {
        struct ib_uverbs_event *evt, *tmp;
 
@@ -142,20 +141,21 @@ void ib_uverbs_release_ucq(struct ib_uverbs_file *file,
                uverbs_uobject_put(&ev_file->uobj);
        }
 
-       ib_uverbs_release_uevent(file, &uobj->uevent);
+       ib_uverbs_release_uevent(&uobj->uevent);
 }
 
-void ib_uverbs_release_uevent(struct ib_uverbs_file *file,
-                             struct ib_uevent_object *uobj)
+void ib_uverbs_release_uevent(struct ib_uevent_object *uobj)
 {
+       struct ib_uverbs_async_event_file *async_file =
+               READ_ONCE(uobj->uobject.ufile->async_file);
        struct ib_uverbs_event *evt, *tmp;
 
-       spin_lock_irq(&file->async_file->ev_queue.lock);
+       spin_lock_irq(&async_file->ev_queue.lock);
        list_for_each_entry_safe(evt, tmp, &uobj->event_list, obj_list) {
                list_del(&evt->list);
                kfree(evt);
        }
-       spin_unlock_irq(&file->async_file->ev_queue.lock);
+       spin_unlock_irq(&async_file->ev_queue.lock);
 }
 
 void ib_uverbs_detach_umcast(struct ib_qp *qp,
@@ -420,7 +420,7 @@ ib_uverbs_async_handler(struct ib_uverbs_async_event_file *async_file,
 static void uverbs_uobj_event(struct ib_uevent_object *eobj,
                              struct ib_event *event)
 {
-       ib_uverbs_async_handler(eobj->uobject.ufile->async_file,
+       ib_uverbs_async_handler(READ_ONCE(eobj->uobject.ufile->async_file),
                                eobj->uobject.user_handle, event->event,
                                &eobj->event_list, &eobj->events_reported);
 }
@@ -476,9 +476,9 @@ void ib_uverbs_init_async_event_file(
        ib_uverbs_init_event_queue(&async_file->ev_queue);
 
        if (!WARN_ON(uverbs_file->async_file)) {
-               uverbs_file->async_file = async_file;
                /* Pairs with the put in ib_uverbs_release_file */
                uverbs_uobject_get(&async_file->uobj);
+               smp_store_release(&uverbs_file->async_file, async_file);
        }
 
        INIT_IB_EVENT_HANDLER(&async_file->event_handler, ib_dev,
@@ -1156,13 +1156,9 @@ static void ib_uverbs_free_hw_resources(struct ib_uverbs_device *uverbs_dev,
                                        struct ib_device *ib_dev)
 {
        struct ib_uverbs_file *file;
-       struct ib_event event;
 
        /* Pending running commands to terminate */
        uverbs_disassociate_api_pre(uverbs_dev);
-       event.event = IB_EVENT_DEVICE_FATAL;
-       event.element.port_num = 0;
-       event.device = ib_dev;
 
        mutex_lock(&uverbs_dev->lists_mutex);
        while (!list_empty(&uverbs_dev->uverbs_file_list)) {
@@ -1178,9 +1174,8 @@ static void ib_uverbs_free_hw_resources(struct ib_uverbs_device *uverbs_dev,
                 */
                mutex_unlock(&uverbs_dev->lists_mutex);
 
-               if (file->async_file)
-                       ib_uverbs_event_handler(
-                               &file->async_file->event_handler, &event);
+               ib_uverbs_async_handler(READ_ONCE(file->async_file), 0,
+                                       IB_EVENT_DEVICE_FATAL, NULL, NULL);
 
                uverbs_destroy_ufile_hw(file, RDMA_REMOVE_DRIVER_REMOVE);
                kref_put(&file->ref, ib_uverbs_release_file);

diff --git a/drivers/infiniband/core/uverbs_std_types.c b/drivers/infiniband/core/uverbs_std_types.c
index efe70bc..994d874 100644 (file)
--- a/drivers/infiniband/core/uverbs_std_types.c
+++ b/drivers/infiniband/core/uverbs_std_types.c
@@ -105,7 +105,7 @@ static int uverbs_free_qp(struct ib_uobject *uobject,
        if (uqp->uxrcd)
                atomic_dec(&uqp->uxrcd->refcnt);
 
-       ib_uverbs_release_uevent(attrs->ufile, &uqp->uevent);
+       ib_uverbs_release_uevent(&uqp->uevent);
        return ret;
 }
 
@@ -138,7 +138,7 @@ static int uverbs_free_wq(struct ib_uobject *uobject,
        if (ib_is_destroy_retryable(ret, why, uobject))
                return ret;
 
-       ib_uverbs_release_uevent(attrs->ufile, &uwq->uevent);
+       ib_uverbs_release_uevent(&uwq->uevent);
        return ret;
 }
 
@@ -163,7 +163,7 @@ static int uverbs_free_srq(struct ib_uobject *uobject,
                atomic_dec(&us->uxrcd->refcnt);
        }
 
-       ib_uverbs_release_uevent(attrs->ufile, uevent);
+       ib_uverbs_release_uevent(uevent);
        return ret;
 }
 

diff --git a/drivers/infiniband/core/uverbs_std_types_cq.c b/drivers/infiniband/core/uverbs_std_types_cq.c
index a41c758..da4110a 100644 (file)
--- a/drivers/infiniband/core/uverbs_std_types_cq.c
+++ b/drivers/infiniband/core/uverbs_std_types_cq.c
@@ -49,7 +49,6 @@ static int uverbs_free_cq(struct ib_uobject *uobject,
                return ret;
 
        ib_uverbs_release_ucq(
-               attrs->ufile,
                ev_queue ? container_of(ev_queue,
                                        struct ib_uverbs_completion_event_file,
                                        ev_queue) :