[IB] uverbs: Avoid NULL pointer deref on CQ async event

Userspace CQs that have no completion event channel attached end up
with their cq_context set to NULL.  However, asynchronous events like
"CQ overrun" can still occur on such CQs, so add a uverbs_file member
to struct ib_ucq_object that we can follow to deliver these events.

Signed-off-by: Roland Dreier <rolandd@cisco.com>

3 files changed, 5 insertions, 6 deletions

diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h
index 031cdf3c066d..ecb830127865 100644
--- a/drivers/infiniband/core/uverbs.h
+++ b/drivers/infiniband/core/uverbs.h
@@ -113,6 +113,7 @@ struct ib_uevent_object {
 
 struct ib_ucq_object {
         struct ib_uobject       uobject;
+        struct ib_uverbs_file  *uverbs_file;
         struct list_head        comp_list;
         struct list_head        async_list;
         u32                     comp_events_reported;
diff --git a/drivers/infiniband/core/uverbs_cmd.c b/drivers/infiniband/core/uverbs_cmd.c
index 8c89abc8c764..63a74151c60b 100644
--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -602,6 +602,7 @@ ssize_t ib_uverbs_create_cq(struct ib_uverbs_file *file,
 
         uobj->uobject.user_handle   = cmd.user_handle;
         uobj->uobject.context       = file->ucontext;
+        uobj->uverbs_file           = file;
         uobj->comp_events_reported  = 0;
         uobj->async_events_reported = 0;
         INIT_LIST_HEAD(&uobj->comp_list);
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
index 0eb38f479b39..e58a7b278a00 100644
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -442,13 +442,10 @@ static void ib_uverbs_async_handler(struct ib_uverbs_file *file,
 
 void ib_uverbs_cq_event_handler(struct ib_event *event, void *context_ptr)
 {
-        struct ib_uverbs_event_file *ev_file = context_ptr;
-        struct ib_ucq_object *uobj;
+        struct ib_ucq_object *uobj = container_of(event->element.cq->uobject,
+                                                  struct ib_ucq_object, uobject);
 
-        uobj = container_of(event->element.cq->uobject,
-                            struct ib_ucq_object, uobject);
-
-        ib_uverbs_async_handler(ev_file->uverbs_file, uobj->uobject.user_handle,
+        ib_uverbs_async_handler(uobj->uverbs_file, uobj->uobject.user_handle,
                                 event->event, &uobj->async_list,
                                 &uobj->async_events_reported);