IB/core: Fix use after free in send_leave function

BugLink: http://bugs.launchpad.net/bugs/1631468

commit 68c6bcdd upstream.

The function send_leave sets the member: group->query_id
(group->query_id = ret) after calling the sa_query, but leave_handler
can be executed before the setting and it might delete the group object,
and will get a memory corruption.

Additionally, this patch gets rid of group->query_id variable which is
not used.

Fixes: faec2f7b ('IB/sa: Track multicast join/leave requests')
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/infiniband/core/multicast.c

@@ -106,7 +106,6 @@ struct mcast_group {
 	atomic_t		refcount;
 	enum mcast_group_state	state;
 	struct ib_sa_query	*query;
-	int			query_id;
 	u16			pkey_index;
 	u8			leave_state;
 	int			retries;
@@ -339,11 +338,7 @@ static int send_join(struct mcast_group *group, struct mcast_member *member)
 				       member->multicast.comp_mask,
 				       3000, GFP_KERNEL, join_handler, group,
 				       &group->query);
-	if (ret >= 0) {
-		group->query_id = ret;
-		ret = 0;
-	}
-	return ret;
+	return (ret > 0) ? 0 : ret;
 }
 
 static int send_leave(struct mcast_group *group, u8 leave_state)
@@ -363,11 +358,7 @@ static int send_leave(struct mcast_group *group, u8 leave_state)
 				       IB_SA_MCMEMBER_REC_JOIN_STATE,
 				       3000, GFP_KERNEL, leave_handler,
 				       group, &group->query);
-	if (ret >= 0) {
-		group->query_id = ret;
-		ret = 0;
-	}
-	return ret;
+	return (ret > 0) ? 0 : ret;
 }
 
 static void join_group(struct mcast_group *group, struct mcast_member *member,