netdev - Re: [PATCH net] net_sched: fix qdisc_tree_decrease

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Thu, 03 Dec 2015 14:59:40 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	cwang@...pensource.com, pageexec@...email.hu, dfucini@...il.com,
	netdev@...r.kernel.org, jhs@...atatu.com, spender@...ecurity.net,
	re.emese@...il.com
Subject: Re: [PATCH net] net_sched: fix qdisc_tree_decrease_qlen() races

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 01 Dec 2015 20:08:51 -0800

> From: Eric Dumazet <edumazet@...gle.com>
> 
> qdisc_tree_decrease_qlen() suffers from two problems on multiqueue
> devices.
> 
> One problem is that it updates sch->q.qlen and sch->qstats.drops
> on the mq/mqprio root qdisc, while it should not : Daniele
> reported underflows errors : 
 ...
> mq/mqprio have their own ways to report qlen/drops by folding stats on
> all their queues, with appropriate locking.
> 
> A second problem is that qdisc_tree_decrease_qlen() calls qdisc_lookup()
> without proper locking : concurrent qdisc updates could corrupt the list
> that qdisc_match_from_root() parses to find a qdisc given its handle.
> 
> Fix first problem adding a TCQ_F_NOPARENT qdisc flag that
> qdisc_tree_decrease_qlen() can use to abort its tree traversal,
> as soon as it meets a mq/mqprio qdisc children.
> 
> Second problem can be fixed by RCU protection.
> Qdisc are already freed after RCU grace period, so qdisc_list_add() and
> qdisc_list_del() simply have to use appropriate rcu list variants.
> 
> A future patch will add a per struct netdev_queue list anchor, so that
> qdisc_tree_decrease_qlen() can have more efficient lookups.
> 
> Reported-by: Daniele Fucini <dfucini@...il.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable, thanks Eric!
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html