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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/cls_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/cls_api.c')
-rw-r--r--net/sched/cls_api.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 7e14f14058e..37a18402164 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -401,7 +401,7 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
if ((dev = dev_get_by_index(tcm->tcm_ifindex)) == NULL)
return skb->len;
- read_lock_bh(&qdisc_tree_lock);
+ read_lock(&qdisc_tree_lock);
if (!tcm->tcm_parent)
q = dev->qdisc_sleeping;
else
@@ -458,7 +458,7 @@ errout:
if (cl)
cops->put(q, cl);
out:
- read_unlock_bh(&qdisc_tree_lock);
+ read_unlock(&qdisc_tree_lock);
dev_put(dev);
return skb->len;
}