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Date: Thu, 02 Jul 2009 18:14:23 +0800
From: Amerigo Wang <amwang@redhat.com>
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To: Eric Paris <eparis@redhat.com>
CC: Eric Sandeen <sandeen@redhat.com>, linux-kernel@vger.kernel.org,
       akpm@linux-foundation.org, Eugene Teo <eteo@redhat.com>,
       viro@zeniv.linux.org.uk
Subject: Re: [Patch] allow file truncations when both suid and write  permissions
 set
References: <20090625090146.6616.9720.sendpatchset@localhost.localdomain>	 <4A4BA6F8.7090905@redhat.com> <4A4BB898.10909@redhat.com>	 <7e0fb38c0907011229h328c8c48i55df5e234b7d367d@mail.gmail.com> <1246479341.22562.71.camel@dhcp235-23.rdu.redhat.com>
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Eric Paris wrote:
> So NAK on both Amerigo's and Eric's patch.  ATTR_FORCE is wrong.
> ATTR_FORCE here is going to force the security system to accept ALL of
> the attr changes, not just the ATTR_KILL_SUID and/or ATTR_KILL_SGID you
> |= in from should_remove_suid.
> You need to follow esandeen's recommendation, change file_remove_suid()
> to dentry_remove_suid() and then use dentry_remove_suid() in do_truncate
> instead of what you are currently trying to do (and I think that's
> supposed to be done under the i_mutex right?)
>   
But file_remove_suid() actually adds ATTR_FORCE too, in __remove_suid()...