netdev - Re: [PATCH] sctp: Do not trigger BUG_ON when deleting assoc without primary path

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Message-ID: <52602BA3.5020405@redhat.com>
Date:	Thu, 17 Oct 2013 20:25:39 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Vlad Yasevich <vyasevich@...il.com>
CC:	netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
	Mark Thomas <Mark.Thomas@...aswitch.com>,
	Neil Horman <nhorman@...driver.com>
Subject: Re: [PATCH] sctp: Do not trigger BUG_ON when deleting assoc without
 primary path

On 10/17/2013 08:01 PM, Daniel Borkmann wrote:
> On 10/17/2013 07:30 PM, Vlad Yasevich wrote:
>> It is possible to enter sctp_cmd_delete_tcb() without having a
>> primary path.  The situations this most often happens in is
>> when duplication cookie processing is triggered.  In this
>> case, we are deleting a temporarily created association that
>> is not fully populated.   Additially, at the time we
>> are deleting the offending association, it is really too
>> late to issue a BUG!
>>
>> This was introduced by:
>> commit f9e42b853523cda0732022c2e0473c183f7aec65
>>     net: sctp: sideeffect: throw BUG if primary_path is NULL
>
> Sure, lets remove it, but then we could still get a WARN() [sure,
> better than BUG], if the user at the very same time checks procfs
> through sctp_seq_dump_local_addrs(), see discussion we had here [1]:
>
>   It may trigger the crash later if the user performs some action on the
>   association that touches the primary. That's the reason why I was
>   proposing the checks below.
>
>   With the checks in command interpreter, we are only left with the
>   possibility that primary_path changes to NULL during the association
>   lifetime, which code audit doesn't support right now.  If that ever
>   changes we would at least have a bit more information to go on.
>
>   [1] http://patchwork.ozlabs.org/patch/251099/

Meaning, all I'm saying is that with f9e42b853 we wanted to find exactly
such a case we have right now, that is, that an assoc could enter the
hashtable w/o primary path, no?
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