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authorPatrick McHardy <kaber@trash.net>2006-09-27 16:45:45 -0700
committerDavid S. Miller <davem@sunset.davemloft.net>2006-09-28 18:01:50 -0700
commit85670cc1faa2e1472e4a423cbf0b5e3d55c5ba88 (patch)
treea5da67836995f1b04c844071db97608bc2c37b85 /net/sched/sch_api.c
parent787e0617e5176176c494a787f1b0a5248a3db568 (diff)
[NET_SCHED]: Fix fallout from dev->qdisc RCU change
The move of qdisc destruction to a rcu callback broke locking in the entire qdisc layer by invalidating previously valid assumptions about the context in which changes to the qdisc tree occur. The two assumptions were: - since changes only happen in process context, read_lock doesn't need bottem half protection. Now invalid since destruction of inner qdiscs, classifiers, actions and estimators happens in the RCU callback unless they're manually deleted, resulting in dead-locks when read_lock in process context is interrupted by write_lock_bh in bottem half context. - since changes only happen under the RTNL, no additional locking is necessary for data not used during packet processing (f.e. u32_list). Again, since destruction now happens in the RCU callback, this assumption is not valid anymore, causing races while using this data, which can result in corruption or use-after-free. Instead of "fixing" this by disabling bottem halfs everywhere and adding new locks/refcounting, this patch makes these assumptions valid again by moving destruction back to process context. Since only the dev->qdisc pointer is protected by RCU, but ->enqueue and the qdisc tree are still protected by dev->qdisc_lock, destruction of the tree can be performed immediately and only the final free needs to happen in the rcu callback to make sure dev_queue_xmit doesn't access already freed memory. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_api.c')
-rw-r--r--net/sched/sch_api.c16
1 files changed, 8 insertions, 8 deletions
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index a19eff12cf7..0b648929114 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -195,14 +195,14 @@ struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle)
{
struct Qdisc *q;
- read_lock_bh(&qdisc_tree_lock);
+ read_lock(&qdisc_tree_lock);
list_for_each_entry(q, &dev->qdisc_list, list) {
if (q->handle == handle) {
- read_unlock_bh(&qdisc_tree_lock);
+ read_unlock(&qdisc_tree_lock);
return q;
}
}
- read_unlock_bh(&qdisc_tree_lock);
+ read_unlock(&qdisc_tree_lock);
return NULL;
}
@@ -837,7 +837,7 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
continue;
if (idx > s_idx)
s_q_idx = 0;
- read_lock_bh(&qdisc_tree_lock);
+ read_lock(&qdisc_tree_lock);
q_idx = 0;
list_for_each_entry(q, &dev->qdisc_list, list) {
if (q_idx < s_q_idx) {
@@ -846,12 +846,12 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
}
if (tc_fill_qdisc(skb, q, q->parent, NETLINK_CB(cb->skb).pid,
cb->nlh->nlmsg_seq, NLM_F_MULTI, RTM_NEWQDISC) <= 0) {
- read_unlock_bh(&qdisc_tree_lock);
+ read_unlock(&qdisc_tree_lock);
goto done;
}
q_idx++;
}
- read_unlock_bh(&qdisc_tree_lock);
+ read_unlock(&qdisc_tree_lock);
}
done:
@@ -1074,7 +1074,7 @@ static int tc_dump_tclass(struct sk_buff *skb, struct netlink_callback *cb)
s_t = cb->args[0];
t = 0;
- read_lock_bh(&qdisc_tree_lock);
+ read_lock(&qdisc_tree_lock);
list_for_each_entry(q, &dev->qdisc_list, list) {
if (t < s_t || !q->ops->cl_ops ||
(tcm->tcm_parent &&
@@ -1096,7 +1096,7 @@ static int tc_dump_tclass(struct sk_buff *skb, struct netlink_callback *cb)
break;
t++;
}
- read_unlock_bh(&qdisc_tree_lock);
+ read_unlock(&qdisc_tree_lock);
cb->args[0] = t;