linux-kernel - Re: [PATCH] prctl: remove one-shot limitation for changing exe link

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Message-ID: <080e133d-cf73-33bc-a5ef-743384dd9465@virtuozzo.com>
Date:	Wed, 20 Jul 2016 13:30:25 +0200
From:	Stanislav Kinsburskiy <skinsbursky@...tuozzo.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Cyrill Gorcunov <gorcunov@...il.com>, <peterz@...radead.org>,
	<mingo@...hat.com>, <mhocko@...e.com>, <keescook@...omium.org>,
	<linux-kernel@...r.kernel.org>, <mguzik@...hat.com>,
	<bsegall@...gle.com>, <john.stultz@...aro.org>, <oleg@...hat.com>,
	<matthltc@...ibm.com>, <akpm@...ux-foundation.org>,
	<luto@...capital.net>, <vbabka@...e.cz>, <xemul@...tuozzo.com>
Subject: Re: [PATCH] prctl: remove one-shot limitation for changing exe link



18.07.2016 22:11, One Thousand Gnomes пишет:
>>>> 1) Attach to process via ptrace (protected by CAP_SYS_PTRACE)
>>>> 2) Unmap all the process file mappings, related to "exe" file.
>>>> 3) Change exe link (protected by CAP_SYS_RESOURCE).
>>>>
>>>> IOW, some other process already has an access to process internals (and thus
>>>> it's already compromised), and can inject fork and use the child of the
>>>> compromised program to masquerade.
>>>> Which means this limitation doesn't solve the problem it was aimed to.
> IFF it is the same uid or root (in which case you already lost). In the
> case of cross uid activity this is not true.

Could you elaborate on it, please?

> Alan