linux-kernel - Re: [PATCHv2 0/2] introduce get_task_exe_file and use it to fix audit_exe

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Date:   Tue, 30 Aug 2016 14:50:21 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Mateusz Guzik <mguzik@...hat.com>
Cc:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        ebiederm@...ssion.com, oleg@...hat.com, sgrubb@...hat.com,
        pmoore@...hat.com, eparis@...hat.com, luto@...capital.net,
        linux-audit@...hat.com, linux-kernel@...r.kernel.org,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCHv2 0/2] introduce get_task_exe_file and use it to fix
 audit_exe_compare

On 2016-08-23 16:20, Mateusz Guzik wrote:
> audit_exe_compare directly accesses mm->exe_file without making sure the
> object is stable. Fixing it using current primitives results in
> partially duplicating what proc_exe_link is doing.
> 
> As such, introduce a trivial helper which can be used in both places and
> fix the func.
> 
> Changes since v1:
> * removed an unused 'out' label which crept in
> 
> Mateusz Guzik (2):
>   mm: introduce get_task_exe_file
>   audit: fix exe_file access in audit_exe_compare

The task_lock affects a much bigger struct than the mm ref count.  Is
this really necessary?  Is a spin-lock significantly lower cost than a
refcount?  Other than that, this refactorization looks sensible.

Acked-by: Richard Guy Briggs <rgb@...hat.com>

>  fs/proc/base.c       |  7 +------
>  include/linux/mm.h   |  1 +
>  kernel/audit_watch.c |  8 +++++---
>  kernel/fork.c        | 23 +++++++++++++++++++++++
>  4 files changed, 30 insertions(+), 9 deletions(-)
> 
> -- 
> 1.8.3.1
> 

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Kernel Security Engineering, Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635