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From: Aleksa Sarai <cyphar@cyphar.com>
To: Jeff Layton <jlayton@kernel.org>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	Al Viro <viro@zeniv.linux.org.uk>, Arnd Bergmann <arnd@arndb.de>,
	Shuah Khan <shuah@kernel.org>
Cc: David Howells <dhowells@redhat.com>,
	Andy Lutomirski <luto@kernel.org>,
	Christian Brauner <christian@brauner.io>,
	Eric Biederman <ebiederm@xmission.com>,
	Aleksa Sarai <cyphar@cyphar.com>, Tycho Andersen <tycho@tycho.ws>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org,
	dev@opencontainers.org, containers@lists.linux-foundation.org
Subject: Re: [PATCH 1/3] namei: implement O_BENEATH-style AT_* flags
Date: Sun, 30 Sep 2018 14:38:23 +1000
Message-ID: <20180930043823.2pgzrtgcziaou7ov@ryuk> (raw)
In-Reply-To: <20180929103453.12025-2-cyphar@cyphar.com>


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On 2018-09-29, Aleksa Sarai <cyphar@cyphar.com> wrote:
> * AT_XDEV: Disallow mount-point crossing (both *down* into one, or *up*
>   from one). The primary "scoping" use is to blocking resolution that
>   crosses a bind-mount, which has a similar property to a symlink (in
>   the way that it allows for escape from the starting-point). Since it
>   is not possible to differentiate bind-mounts However since
>   bind-mounting requires privileges (in ways symlinks don't) this has
>   been split from LOOKUP_BENEATH. The naming is based on "find -xdev"
>   (though find(1) doesn't walk upwards, the semantics seem obvious).

I've just noticed that the mountpoint-crossing code for AT_XDEV doesn't
detect things like:

   % ln -s / /tmp/jumpup
   % vfs_helper -o open -F xdev -d /tmp jumpup
   /

I will fix that in v2.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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  parent reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-29 10:34 [PATCH 0/3] namei: implement various scoping " Aleksa Sarai
2018-09-29 10:34 ` [PATCH 1/3] namei: implement O_BENEATH-style " Aleksa Sarai
2018-09-29 14:48   ` Christian Brauner
2018-09-29 15:34     ` Aleksa Sarai
2018-09-30  4:38   ` Aleksa Sarai [this message]
2018-10-01 12:28   ` Jann Horn
2018-10-01 13:00     ` Christian Brauner
2018-10-01 16:04       ` Aleksa Sarai
2018-10-04 17:20         ` Christian Brauner
2018-09-29 13:15 ` [PATCH 2/3] namei: implement AT_THIS_ROOT chroot-like path resolution Aleksa Sarai
2018-09-29 13:15   ` [PATCH 3/3] selftests: vfs: add AT_* path resolution tests Aleksa Sarai
2018-09-29 16:35   ` [PATCH 2/3] namei: implement AT_THIS_ROOT chroot-like path resolution Jann Horn
2018-09-29 17:25     ` Andy Lutomirski
2018-10-01  9:46       ` Aleksa Sarai
2018-10-01  5:44     ` Aleksa Sarai
2018-10-01 10:13       ` Jann Horn
2018-10-01 16:18         ` Aleksa Sarai
2018-10-04 17:27           ` Christian Brauner
2018-10-01 10:42       ` Christian Brauner
2018-10-01 11:29         ` Jann Horn
2018-10-01 12:35           ` Christian Brauner
2018-10-01 13:55       ` Bruce Fields
2018-10-01 14:28       ` Andy Lutomirski
2018-10-02  7:32         ` Aleksa Sarai
2018-10-03 22:09           ` Andy Lutomirski
2018-10-06 20:56           ` Florian Weimer
2018-10-06 21:49             ` Christian Brauner
2018-10-01 14:00     ` Christian Brauner
2018-10-04 16:26     ` Aleksa Sarai
2018-10-04 17:31       ` Christian Brauner
2018-10-04 18:26       ` Jann Horn
2018-10-05 15:07         ` Aleksa Sarai
2018-10-05 15:55           ` Jann Horn
2018-10-06  2:10             ` Aleksa Sarai
2018-10-08 10:50               ` Jann Horn
2018-09-29 14:25 ` [PATCH 0/3] namei: implement various scoping AT_* flags Andy Lutomirski
2018-09-29 15:45   ` Aleksa Sarai
2018-09-29 16:34     ` Andy Lutomirski
2018-09-29 19:44       ` Matthew Wilcox
2018-09-29 14:38 ` Christian Brauner
2018-09-30  4:44   ` Aleksa Sarai
2018-09-30 13:54 ` Alban Crequy
2018-09-30 14:02   ` Christian Brauner
2018-09-30 19:45 ` Mickaël Salaün
2018-09-30 21:46   ` Jann Horn
2018-09-30 22:37     ` Mickaël Salaün
2018-10-01 20:14       ` James Morris
2018-10-01  4:08 ` Dave Chinner
2018-10-01  5:47   ` Aleksa Sarai
2018-10-01  6:14     ` Dave Chinner
2018-10-01 13:28 ` David Laight
2018-10-01 16:15   ` Aleksa Sarai
2018-10-03 13:21     ` David Laight

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