linux-kernel - Re: [nsproxy] BUG: unable to handle kernel NULL pointer dereference at 0000000000000024

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Message-ID: <CADZ9YHhPq7aWwmyBoEt+CsGnKfKTeZN1bCT-LtwtJxUaHGwJ=g@mail.gmail.com>
Date:	Sat, 9 Mar 2013 09:54:45 +0600
From:	Rakib Mullick <rakib.mullick@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Fengguang Wu <fengguang.wu@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [nsproxy] BUG: unable to handle kernel NULL pointer dereference
 at 0000000000000024

On Fri, Mar 8, 2013 at 10:01 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
>
> When a new task is created one of two things needs to happen.
> A) A reference count needs to be added to the current nsproxy.
> B) B a new nsproxy needs to be created.
>
> The way that code works today is far from a shiny example of totally
> clear code but it is not incorrect.
>
> By moving get_nsproxy down below the first return 0, you removed taking
> the reference count in the one case it is important.
>
> Arguably we should apply the patch below for clarity, and I just might
> queue it up for 3.10.
>
This one is much more cleaner. One thing regarding this patch, can we
check the namespace related flags at copy_namespace() call time at
copy_process(), also get_nsproxy()? I think this will reduce some
extra function call overhead and as you've mentioned get_nsproxy() is
needed at every process creation.

Thanks,
Rakib
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