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From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: David Miller <davem@davemloft.net>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Linux Kernel Network Developers <netdev@vger.kernel.org>,
	brouer@redhat.com
Subject: Re: [net-next PATCH 1/3] Revert "icmp: avoid allocating large struct on stack"
Date: Tue, 10 Jan 2017 21:08:20 +0100	[thread overview]
Message-ID: <20170110210820.1c5dbc87@redhat.com> (raw)
In-Reply-To: <CAM_iQpV0V23fndi6DOW1gu9kq+2UufHNrnfRYCME7uOOLCaX-Q@mail.gmail.com>


On Tue, 10 Jan 2017 10:44:59 -0800 Cong Wang <xiyou.wangcong@gmail.com> wrote:

> On Tue, Jan 10, 2017 at 10:12 AM, David Miller <davem@davemloft.net> wrote:
[...]
> > You can keep showing us how expertly you can deflect the real
> > issue we are discussion here, but that won't improve the situation
> > at all I am afraid.  
> 
> Of course, there are just too many people too lazy to do a google search:
> 
> https://lists.debian.org/debian-kernel/2013/05/msg00500.html

My analysis of the problem shown in above link is not related to using
all the stack space, but instead that skb->cb was not cleared.  This
can cause the ip_options_echo() call in icmp_send() to access garbage
as this is: __ip_options_echo(dopt, skb, &IPCB(skb)->opt).

Fixed by commit a622260254ee ("ip_tunnel: fix kernel panic with icmp_dest_unreach")
 https://git.kernel.org/torvalds/c/a622260254ee

Thus, it is (likely) the __ip_options_echo() call that violates stack
access, as it is passed in a pointer to the stack, and advance this
based on garbage "optlen".

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer

  parent reply	other threads:[~2017-01-10 20:08 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-09 15:03 [net-next PATCH 0/3] net: optimize ICMP-reply code path Jesper Dangaard Brouer
2017-01-09 15:04 ` [net-next PATCH 1/3] Revert "icmp: avoid allocating large struct on stack" Jesper Dangaard Brouer
2017-01-09 17:42   ` Cong Wang
2017-01-09 17:50     ` Eric Dumazet
2017-01-09 17:59       ` Cong Wang
2017-01-09 18:07         ` Eric Dumazet
2017-01-09 18:52           ` David Miller
2017-01-09 20:53             ` Jesper Dangaard Brouer
2017-01-10 18:06             ` Cong Wang
2017-01-10 18:12               ` David Miller
2017-01-10 18:44                 ` Cong Wang
2017-01-10 18:48                   ` Cong Wang
2017-01-10 18:54                   ` David Miller
2017-01-12 22:46                     ` Cong Wang
2017-01-10 20:08                   ` Jesper Dangaard Brouer [this message]
2017-01-10 21:48                     ` Eric Dumazet
2017-01-12 22:21                       ` Cong Wang
2017-01-10 21:41                 ` Joe Perches
2017-01-09 19:33           ` Joe Perches
2017-01-10 18:01           ` Cong Wang
2017-01-09 18:47         ` David Miller
2017-01-09 17:42   ` Eric Dumazet
2017-01-09 15:04 ` [net-next PATCH 2/3] net: reduce cycles spend on ICMP replies that gets rate limited Jesper Dangaard Brouer
2017-01-09 17:44   ` Eric Dumazet
2017-01-11 17:15     ` Eric Dumazet
2017-06-04  7:11   ` Florian Weimer
2017-06-04 14:38     ` Jesper Dangaard Brouer
2017-06-05 14:22       ` Florian Weimer
2017-01-09 15:04 ` [net-next PATCH 3/3] net: for rate-limited ICMP replies save one atomic operation Jesper Dangaard Brouer
2017-01-09 17:44   ` Eric Dumazet
2017-01-09 17:43 ` [net-next PATCH 0/3] net: optimize ICMP-reply code path Cong Wang
2017-01-09 17:56   ` Eric Dumazet
2017-01-09 20:49 ` David Miller

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