diff options
| author | Jarek Poplawski <jarkao2@gmail.com> | 2009-03-15 20:00:19 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2009-03-15 20:00:19 -0700 |
| commit | 7cd0a63872ac6ef97265f07adc367ca4f984468e (patch) | |
| tree | 44265aa422b3133b07eee87280cca3c89225437a | |
| parent | 8bdd663aba341c15cd2fa9dbd7061b8b387964dc (diff) | |
| download | linux-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>
| -rw-r--r-- | net/sched/sch_cbq.c | 7 | ||||
| -rw-r--r-- | net/sched/sch_drr.c | 7 | ||||
| -rw-r--r-- | net/sched/sch_hfsc.c | 7 | ||||
| -rw-r--r-- | net/sched/sch_htb.c | 7 |
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; |