From: Jason Baron <jbaron@akamai•com>
To: Dmitry Vyukov <dvyukov@google•com>, Joe Perches <joe@perches•com>
Cc: Aaron Conole <aconole@redhat•com>,
Andrew Morton <akpm@linux-foundation•org>,
LKML <linux-kernel@vger•kernel.org>,
Eric Dumazet <edumazet@google•com>,
syzkaller <syzkaller@googlegroups•com>,
Vladislav Yasevich <vyasevich@gmail•com>,
linux-sctp@vger•kernel.org, netdev <netdev@vger•kernel.org>,
Kostya Serebryany <kcc@google•com>,
Alexander Potapenko <glider@google•com>,
Sasha Levin <sasha.levin@oracle•com>
Subject: Re: use-after-free in sctp_do_sm
Date: Fri, 4 Dec 2015 11:47:52 -0500 [thread overview]
Message-ID: <5661C3B8.2030902@akamai.com> (raw)
In-Reply-To: <CACT4Y+btkVJBtXkp0QAJhdoK_5TeVJ97GU_wOrMsPNG3E98vaQ@mail.gmail.com>
On 12/04/2015 11:12 AM, Dmitry Vyukov wrote:
> On Thu, Dec 3, 2015 at 9:51 PM, Joe Perches <joe@perches•com> wrote:
>> (adding lkml as this is likely better discussed there)
>>
>> On Thu, 2015-12-03 at 15:42 -0500, Jason Baron wrote:
>>> On 12/03/2015 03:24 PM, Joe Perches wrote:
>>>> On Thu, 2015-12-03 at 15:10 -0500, Jason Baron wrote:
>>>>> On 12/03/2015 03:03 PM, Joe Perches wrote:
>>>>>> On Thu, 2015-12-03 at 14:32 -0500, Jason Baron wrote:
>>>>>>> On 12/03/2015 01:52 PM, Aaron Conole wrote:
>>>>>>>> I think that as a minimum, the following patch should be evaluted,
>>>>>>>> but am unsure to whom I should submit it (after I test):
>>>>>> []
>>>>>>> Agreed - the intention here is certainly to have no side effects. It
>>>>>>> looks like 'no_printk()' is used in quite a few other places that would
>>>>>>> benefit from this change. So we probably want a generic
>>>>>>> 'really_no_printk()' macro.
>>>>>>
>>>>>> https://lkml.org/lkml/2012/6/17/231
>>>>>
>>>>> I don't see this in the tree.
>>>>
>>>> It never got applied.
>>>>
>>>>> Also maybe we should just convert
>>>>> no_printk() to do what your 'eliminated_printk()'.
>>>>
>>>> Some of them at least.
>>>>
>>>>> So we can convert all users with this change?
>>>>
>>>> I don't think so, I think there are some
>>>> function evaluation/side effects that are
>>>> required. I believe some do hardware I/O.
>>>>
>>>> It'd be good to at least isolate them.
>>>>
>>>> I'm not sure how to find them via some
>>>> automated tool/mechanism though.
>>>>
>>>> I asked Julia Lawall about it once in this
>>>> thread: https://lkml.org/lkml/2014/12/3/696
>>>>
>>>
>>> Seems rather fragile to have side effects that we rely
>>> upon hidden in a printk().
>>
>> Yup.
>>
>>> Just convert them and see what breaks :)
>>
>> I appreciate your optimism. It's very 1995.
>> Try it and see what happens.
>
>
> But Aaron says that DYNAMIC_DEBUG is enabled in most major
> distributions, and all these side-effects don't happen with
> DYNAMIC_DEBUG.
When DYNAMIC_DEBUG is enabled we have this wrapper from
include/linux/dynamic_debug.h:
if (unlikely(descriptor.flags & _DPRINTK_FLAGS_PRINT))
<do debug stuff>
So the compiler is not emitting the side-effects in this
case.
>This suggests that we can make these side-effects not
> happen without DYNAMIC_DEBUG as well.
> Or I am missing something here?
>
When DYNAMIC_DEBUG is disabled we are instead replacing
pr_debug() with the 'no_printk()' function as you've pointed
out. We are changing this to emit no code at all:
http://marc.info/?l=linux-kernel&m=144918276518878&w=2
Thanks,
-Jason
next prev parent reply other threads:[~2015-12-04 16:47 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-24 9:15 use-after-free in sctp_do_sm Dmitry Vyukov
2015-11-24 9:31 ` Dmitry Vyukov
2015-11-24 10:10 ` Dmitry Vyukov
2015-11-24 20:45 ` Neil Horman
2015-11-24 21:08 ` Eric Dumazet
2015-11-24 21:12 ` David Miller
2015-11-25 15:12 ` Vlad Yasevich
2015-11-28 15:50 ` Dmitry Vyukov
2015-12-03 16:51 ` Marcelo Ricardo Leitner
2015-12-03 17:43 ` Marcelo Ricardo Leitner
2015-12-03 17:59 ` Eric Dumazet
2015-12-03 18:06 ` Marcelo
2015-12-03 18:35 ` Vlad Yasevich
2015-12-03 18:43 ` Marcelo
2015-12-04 17:14 ` [PATCH net 0/3] sctp: packet timestamp fixes Marcelo Ricardo Leitner
2015-12-04 17:14 ` [PATCH net 1/3] sctp: use the same clock as if sock source timestamps were on Marcelo Ricardo Leitner
2015-12-04 20:31 ` Vlad Yasevich
2015-12-04 17:14 ` [PATCH net 2/3] sctp: update the netstamp_needed counter when copying sockets Marcelo Ricardo Leitner
2015-12-04 20:33 ` Vlad Yasevich
2015-12-04 17:14 ` [PATCH net 3/3] sctp: also copy sk_tsflags when copying the socket Marcelo Ricardo Leitner
2015-12-04 20:33 ` Vlad Yasevich
2015-12-06 3:24 ` [PATCH net 0/3] sctp: packet timestamp fixes David Miller
2015-12-03 13:05 ` use-after-free in sctp_do_sm Marcelo Ricardo Leitner
2015-12-03 13:45 ` Dmitry Vyukov
2015-12-03 14:48 ` Eric Dumazet
2015-12-03 15:55 ` Dmitry Vyukov
2015-12-03 16:15 ` Marcelo Ricardo Leitner
2015-12-03 17:02 ` Eric Dumazet
2015-12-03 17:12 ` Dmitry Vyukov
2015-12-03 18:52 ` Aaron Conole
2015-12-03 19:06 ` Joe Perches
2015-12-03 19:32 ` Jason Baron
2015-12-03 20:03 ` Joe Perches
2015-12-03 20:10 ` Jason Baron
2015-12-03 20:24 ` Joe Perches
2015-12-03 20:42 ` Jason Baron
2015-12-03 20:51 ` Joe Perches
2015-12-04 10:40 ` Dmitry Vyukov
2015-12-04 12:55 ` Marcelo Ricardo Leitner
2015-12-04 15:37 ` Vlad Yasevich
2015-12-04 15:51 ` Aaron Conole
2015-12-04 16:12 ` Dmitry Vyukov
2015-12-04 16:47 ` Jason Baron [this message]
2015-12-04 17:03 ` Joe Perches
2015-12-04 17:11 ` Jason Baron
2015-12-04 10:41 ` Dmitry Vyukov
2015-12-04 17:48 ` Marcelo Ricardo Leitner
2015-12-04 20:25 ` Dmitry Vyukov
2015-12-04 21:34 ` Marcelo Ricardo Leitner
2015-12-04 21:38 ` Dmitry Vyukov
2015-12-05 16:39 ` Vlad Yasevich
2015-12-07 11:26 ` Dmitry Vyukov
2015-12-07 13:15 ` Marcelo Ricardo Leitner
2015-12-07 13:20 ` Dmitry Vyukov
2015-12-07 18:52 ` Marcelo Ricardo Leitner
2015-12-07 19:33 ` Vlad Yasevich
2015-12-07 19:50 ` Marcelo Ricardo Leitner
2015-12-07 20:37 ` Vlad Yasevich
2015-12-07 20:52 ` Marcelo Ricardo Leitner
2015-12-08 17:30 ` Dmitry Vyukov
2015-12-08 17:40 ` Marcelo Ricardo Leitner
2015-12-08 19:22 ` Dmitry Vyukov
2015-12-09 14:41 ` Dmitry Vyukov
2015-12-09 15:03 ` Marcelo Ricardo Leitner
2015-12-09 16:41 ` Marcelo Ricardo Leitner
2015-12-11 13:35 ` Dmitry Vyukov
2015-12-11 13:51 ` Marcelo Ricardo Leitner
2015-12-11 14:03 ` Marcelo Ricardo Leitner
2015-12-11 14:30 ` Dmitry Vyukov
2015-12-11 15:55 ` Marcelo Ricardo Leitner
2016-01-08 13:00 ` [PATCH] sctp: fix use-after-free in pr_debug statement Marcelo Ricardo Leitner
2016-01-11 17:00 ` Vlad Yasevich
2016-01-11 22:13 ` David Miller
2016-01-12 8:41 ` Dmitry Vyukov
2015-12-11 18:37 ` use-after-free in sctp_do_sm Vlad Yasevich
2015-12-14 9:50 ` David Laight
2015-12-14 14:25 ` Vlad Yasevich
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