diff options
| author | Cong Wang <xiyou.wangcong@gmail.com> | 2025-04-28 16:29:54 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-08-28 16:24:33 +0200 |
| commit | c2d25fddd867ce20a266806634eeeb5c30cb520c (patch) | |
| tree | 832f233d274e995dc2ec34c912b090ae7bcb6373 /net | |
| parent | eda741fe155ddf5ecd2dd3bfbd4fc3c0c7dbb450 (diff) | |
| download | linux-c2d25fddd867ce20a266806634eeeb5c30cb520c.tar.gz linux-c2d25fddd867ce20a266806634eeeb5c30cb520c.tar.bz2 linux-c2d25fddd867ce20a266806634eeeb5c30cb520c.zip | |
sch_htb: make htb_deactivate() idempotent
commit 3769478610135e82b262640252d90f6efb05be71 upstream.
Alan reported a NULL pointer dereference in htb_next_rb_node()
after we made htb_qlen_notify() idempotent.
It turns out in the following case it introduced some regression:
htb_dequeue_tree():
|-> fq_codel_dequeue()
|-> qdisc_tree_reduce_backlog()
|-> htb_qlen_notify()
|-> htb_deactivate()
|-> htb_next_rb_node()
|-> htb_deactivate()
For htb_next_rb_node(), after calling the 1st htb_deactivate(), the
clprio[prio]->ptr could be already set to NULL, which means
htb_next_rb_node() is vulnerable here.
For htb_deactivate(), although we checked qlen before calling it, in
case of qlen==0 after qdisc_tree_reduce_backlog(), we may call it again
which triggers the warning inside.
To fix the issues here, we need to:
1) Make htb_deactivate() idempotent, that is, simply return if we
already call it before.
2) Make htb_next_rb_node() safe against ptr==NULL.
Many thanks to Alan for testing and for the reproducer.
Fixes: 5ba8b837b522 ("sch_htb: make htb_qlen_notify() idempotent")
Reported-by: Alan J. Wylie <alan@wylie.me.uk>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Link: https://patch.msgid.link/20250428232955.1740419-2-xiyou.wangcong@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Siddh Raman Pant <siddh.raman.pant@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/sched/sch_htb.c | 15 |
1 files changed, 6 insertions, 9 deletions
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c index cf835130f891..e9f349cb6446 100644 --- a/net/sched/sch_htb.c +++ b/net/sched/sch_htb.c @@ -345,7 +345,8 @@ static void htb_add_to_wait_tree(struct htb_sched *q, */ static inline void htb_next_rb_node(struct rb_node **n) { - *n = rb_next(*n); + if (*n) + *n = rb_next(*n); } /** @@ -606,8 +607,8 @@ static inline void htb_activate(struct htb_sched *q, struct htb_class *cl) */ static inline void htb_deactivate(struct htb_sched *q, struct htb_class *cl) { - WARN_ON(!cl->prio_activity); - + if (!cl->prio_activity) + return; htb_deactivate_prios(q, cl); cl->prio_activity = 0; } @@ -1506,8 +1507,6 @@ static void htb_qlen_notify(struct Qdisc *sch, unsigned long arg) { struct htb_class *cl = (struct htb_class *)arg; - if (!cl->prio_activity) - return; htb_deactivate(qdisc_priv(sch), cl); } @@ -1762,8 +1761,7 @@ static int htb_delete(struct Qdisc *sch, unsigned long arg, if (cl->parent) cl->parent->children--; - if (cl->prio_activity) - htb_deactivate(q, cl); + htb_deactivate(q, cl); if (cl->cmode != HTB_CAN_SEND) htb_safe_rb_erase(&cl->pq_node, @@ -1975,8 +1973,7 @@ static int htb_change_class(struct Qdisc *sch, u32 classid, /* turn parent into inner node */ qdisc_purge_queue(parent->leaf.q); parent_qdisc = parent->leaf.q; - if (parent->prio_activity) - htb_deactivate(q, parent); + htb_deactivate(q, parent); /* remove from evt list because of level change */ if (parent->cmode != HTB_CAN_SEND) { |