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authorJarek Poplawski <jarkao2@gmail.com>2009-03-15 20:00:19 -0700
committerDavid S. Miller <davem@davemloft.net>2009-03-15 20:00:19 -0700
commit7cd0a63872ac6ef97265f07adc367ca4f984468e (patch)
tree44265aa422b3133b07eee87280cca3c89225437a /net/sched
parent8bdd663aba341c15cd2fa9dbd7061b8b387964dc (diff)
downloadlinux-7cd0a63872ac6ef97265f07adc367ca4f984468e.tar.bz2
pkt_sched: Change misleading code in class delete.
While looking for a possible reason of bugzilla report on HTB oops: http://bugzilla.kernel.org/show_bug.cgi?id=12858 I found the code in htb_delete calling htb_destroy_class on zero refcount is very misleading: it can suggest this is a common path, and destroy is called under sch_tree_lock. Actually, this can never happen like this because before deletion cops->get() is done, and after delete a class is still used by tclass_notify. The class destroy is always called from cops->put(), so without sch_tree_lock. This doesn't mean much now (since 2.6.27) because all vulnerable calls were moved from htb_destroy_class to htb_delete, but there was a bug in older kernels. The same change is done for other classful scheds, which, it seems, didn't have similar locking problems here. Reported-by: m0sia <m0sia@m0sia.ru> Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
-rw-r--r--net/sched/sch_cbq.c7
-rw-r--r--net/sched/sch_drr.c7
-rw-r--r--net/sched/sch_hfsc.c7
-rw-r--r--net/sched/sch_htb.c7
4 files changed, 20 insertions, 8 deletions
diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index 9e43ed949167..d728d8111732 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -1960,8 +1960,11 @@ static int cbq_delete(struct Qdisc *sch, unsigned long arg)
cbq_rmprio(q, cl);
sch_tree_unlock(sch);
- if (--cl->refcnt == 0)
- cbq_destroy_class(sch, cl);
+ BUG_ON(--cl->refcnt == 0);
+ /*
+ * This shouldn't happen: we "hold" one cops->get() when called
+ * from tc_ctl_tclass; the destroy method is done from cops->put().
+ */
return 0;
}
diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index e36e94ab4e10..7597fe146866 100644
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -155,8 +155,11 @@ static int drr_delete_class(struct Qdisc *sch, unsigned long arg)
drr_purge_queue(cl);
qdisc_class_hash_remove(&q->clhash, &cl->common);
- if (--cl->refcnt == 0)
- drr_destroy_class(sch, cl);
+ BUG_ON(--cl->refcnt == 0);
+ /*
+ * This shouldn't happen: we "hold" one cops->get() when called
+ * from tc_ctl_tclass; the destroy method is done from cops->put().
+ */
sch_tree_unlock(sch);
return 0;
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index 74226b265528..5022f9c1f34b 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1139,8 +1139,11 @@ hfsc_delete_class(struct Qdisc *sch, unsigned long arg)
hfsc_purge_queue(sch, cl);
qdisc_class_hash_remove(&q->clhash, &cl->cl_common);
- if (--cl->refcnt == 0)
- hfsc_destroy_class(sch, cl);
+ BUG_ON(--cl->refcnt == 0);
+ /*
+ * This shouldn't happen: we "hold" one cops->get() when called
+ * from tc_ctl_tclass; the destroy method is done from cops->put().
+ */
sch_tree_unlock(sch);
return 0;
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 355974f610c5..88cd02626621 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1275,8 +1275,11 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg)
if (last_child)
htb_parent_to_leaf(q, cl, new_q);
- if (--cl->refcnt == 0)
- htb_destroy_class(sch, cl);
+ BUG_ON(--cl->refcnt == 0);
+ /*
+ * This shouldn't happen: we "hold" one cops->get() when called
+ * from tc_ctl_tclass; the destroy method is done from cops->put().
+ */
sch_tree_unlock(sch);
return 0;