Re: [BUG] act_ife: sleeping functions called in atomic context

[Jamal Hadi Salim]

On 16-06-16 05:43 PM, Cong Wang wrote:

On Thu, Jun 16, 2016 at 1:50 PM, Alexey Khoroshilov
<khoroshi...@ispras.ru> wrote:

tcf_ife_init() contains a big chunk of code executed with
ife->tcf_lock spinlock held. But that code contains several calls
to sleeping functions:
   populate_metalist() and use_all_metadata()
     -> add_metainfo()
       -> find_ife_oplist(metaid)
         -> read_lock()
         -> try_module_get(o->owner)
       -> kzalloc(sizeof(*mi), GFP_KERNEL);

Hmm, we don't need to hold that spinlock when we create a new ife action,
since we haven't inserted it yet. We do need it when we modify an existing
one. So I am thinking if we can refactor that code to avoid spinlock
whenever possible.

Does attached (compile tested) patch help?

       -> ops->alloc(mi, metaval);
       -> module_put(ops->owner);
   _tcf_ife_cleanup()
     -> module_put()

The same problem is actual for tcf_ife_cleanup() as well.

Huh? Both module_put() and kfree() should not sleep, right?

I dont think there is any sleeping there ;->

cheers,
jamal

diff --git a/net/sched/act_ife.c b/net/sched/act_ife.c
index 6bbc518..e341bef 100644
--- a/net/sched/act_ife.c
+++ b/net/sched/act_ife.c
@@ -302,7 +302,9 @@ static int add_metainfo(struct tcf_ife_info *ife, u32 
metaid, void *metaval,
                }
        }
 
+       spin_lock_bh(&ife->tcf_lock);
        list_add_tail(&mi->metalist, &ife->metalist);
+       spin_unlock_bh(&ife->tcf_lock);
 
        return ret;
 }
@@ -474,7 +476,6 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
                        saddr = nla_data(tb[TCA_IFE_SMAC]);
        }
 
-       spin_lock_bh(&ife->tcf_lock);
        ife->tcf_action = parm->action;
 
        if (parm->flags & IFE_ENCODE) {
@@ -504,7 +505,6 @@ metadata_parse_err:
                        if (ret == ACT_P_CREATED)
                                _tcf_ife_cleanup(a, bind);
 
-                       spin_unlock_bh(&ife->tcf_lock);
                        return err;
                }
 
@@ -523,13 +523,10 @@ metadata_parse_err:
                        if (ret == ACT_P_CREATED)
                                _tcf_ife_cleanup(a, bind);
 
-                       spin_unlock_bh(&ife->tcf_lock);
                        return err;
                }
        }
 
-       spin_unlock_bh(&ife->tcf_lock);
-
        if (ret == ACT_P_CREATED)
                tcf_hash_insert(tn, a);