linux-kernel - Re: One process with multiple user ids.

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Message-ID: <Pine.LNX.4.64.0710021349440.7130@fbirervta.pbzchgretzou.qr>
Date:	Tue, 2 Oct 2007 13:52:33 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...putergmbh.de>
To:	Giuliano Gagliardi <gogi-k@...i.tv>
cc:	linux-kernel@...r.kernel.org
Subject: Re: One process with multiple user ids.

On Oct 2 2007 13:39, Giuliano Gagliardi wrote:
>>
>> You could write up a LSM that restricts UID changing.
>
>Would you not consider it more useful to let one process have multiple user 
>ids? I do not see why they can have multiple group ids, but only (and 
>exactly) three user ids.

It would raise the complexity enormously. In the kernel, you
currently do if (current->uid == inode->i_uid) or so. If you were to
have multiple identities, that would evolve into a costly "if
(in_user_p(inode->i_uid))" or so, much like in_group_p does it at the
moment.
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