[PATCH] IB: fix use-after-free in user verbs cleanup

[Roland Dreier <rolandd@cisco.com>]

Hi Andrew,

I'd like to get this into 2.6.13 if possible.  If it's too late, it's
not the end of the world -- we can wait for 2.6.13.1.  But it's a
tiny, obvious patch that fixes a crash that at least one person
actually hit running a normal application:
http://openib.org/pipermail/openib-general/2005-August/010248.html

Thanks,
  Roland


Fix a use-after-free bug in userspace verbs cleanup: we can't touch
mr->device after we free mr by calling ib_dereg_mr().

diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
--- a/drivers/infiniband/core/uverbs_main.c
+++ b/drivers/infiniband/core/uverbs_main.c
@@ -130,13 +130,14 @@ static int ib_dealloc_ucontext(struct ib
 
 	list_for_each_entry_safe(uobj, tmp, &context->mr_list, list) {
 		struct ib_mr *mr = idr_find(&ib_uverbs_mr_idr, uobj->id);
+		struct ib_device *mrdev = mr->device;
 		struct ib_umem_object *memobj;
 
 		idr_remove(&ib_uverbs_mr_idr, uobj->id);
 		ib_dereg_mr(mr);
 
 		memobj = container_of(uobj, struct ib_umem_object, uobject);
-		ib_umem_release_on_close(mr->device, &memobj->umem);
+		ib_umem_release_on_close(mrdev, &memobj->umem);
 
 		list_del(&uobj->list);
 		kfree(memobj);