netdev - Re: [PATCH net] rtnl: limit IFLA_NUM_TX_QUEUES and IFLA_NUM_RX

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Date:   Tue, 02 Oct 2018 16:09:24 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH net] rtnl: limit IFLA_NUM_TX_QUEUES and
 IFLA_NUM_RX_QUEUES to 4096

From: Eric Dumazet <edumazet@...gle.com>
Date: Tue,  2 Oct 2018 15:47:35 -0700

> We have an impressive number of syzkaller bugs that are linked
> to the fact that syzbot was able to create a networking device
> with millions of TX (or RX) queues.
> 
> Let's limit the number of RX/TX queues to 4096, this really should
> cover all known cases.
> 
> A separate patch will add various cond_resched() in the loops
> handling sysfs entries at device creation and dismantle.
> 
> Tested:
> 
> lpaa6:~# ip link add gre-4097 numtxqueues 4097 numrxqueues 4097 type ip6gretap
> RTNETLINK answers: Invalid argument
> 
> lpaa6:~# time ip link add gre-4096 numtxqueues 4096 numrxqueues 4096 type ip6gretap
> 
> real	0m0.180s
> user	0m0.000s
> sys	0m0.107s
> 
> Fixes: 76ff5cc91935 ("rtnl: allow to specify number of rx and tx queues on device creation")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable.