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From: James Morris <jmorris@namei.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	David Howells <dhowells@redhat.com>,
	linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	torvalds@linux-foundation.org,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH 02/10] vfs: syscall: Add move_mount(2) to move mounts around
Date: Wed, 24 Jul 2019 07:45:07 +1000 (AEST)
Message-ID: <alpine.LRH.2.21.1907240744080.16974@namei.org> (raw)
In-Reply-To: <20190708202124.GX17978@ZenIV.linux.org.uk>

On Mon, 8 Jul 2019, Al Viro wrote:

> On Mon, Jul 08, 2019 at 07:01:32PM +0100, Al Viro wrote:
> > On Mon, Jul 08, 2019 at 12:12:21PM -0500, Eric W. Biederman wrote:
> > 
> > > Al you do realize that the TOCTOU you are talking about comes the system
> > > call API.  TOMOYO can only be faulted for not playing in their own
> > > sandbox and not reaching out and fixing the vfs implementation details.
> 
> PS: the fact that mount(2) has been overloaded to hell and back (including
> MS_MOVE, which goes back to v2.5.0.5) predates the introduction of ->sb_mount()
> and LSM in general (2.5.27).  MS_BIND is 2.4.0-test9pre2.
> 
> In all the years since the introduction of ->sb_mount() I've seen zero
> questions from LSM folks regarding a sane place for those checks.  What I have
> seen was "we want it immediately upon the syscall entry, let the module
> figure out what to do" in reply to several times I tried to tell them "folks,
> it's called in a bad place; you want the checks applied to objects, not to
> raw string arguments".
> 
> As it is, we have easily bypassable checks on mount(2) (by way of ->sb_mount();
> there are other hooks also in the game for remounts and new mounts).

What are your recommendations for placing these checks?

-- 
James Morris
<jmorris@namei.org>


  parent reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-19 17:08 [PATCH 00/10] VFS: Provide new mount UAPI David Howells
2019-02-19 17:08 ` [PATCH 01/10] vfs: syscall: Add open_tree(2) to reference or clone a mount David Howells
2019-02-19 17:08 ` [PATCH 02/10] vfs: syscall: Add move_mount(2) to move mounts around David Howells
2019-02-20 12:32   ` Alan Jenkins
2019-02-20 12:41     ` Alan Jenkins
2019-02-20 16:23   ` Jann Horn
2019-07-08 12:02   ` Tetsuo Handa
2019-07-08 13:18     ` Al Viro
2019-07-08 17:12       ` Eric W. Biederman
2019-07-08 18:01         ` Al Viro
2019-07-08 18:13           ` Al Viro
2019-07-08 20:21           ` Al Viro
2019-07-09  0:13             ` Eric W. Biederman
2019-07-09 10:51               ` Tetsuo Handa
2019-07-22 10:12                 ` Tetsuo Handa
2019-07-23  4:16                   ` John Johansen
2019-07-23 13:45                     ` Tetsuo Handa
2019-08-06 10:43                       ` Tetsuo Handa
2019-08-09 15:44                         ` [PATCH] LSM: Disable move_mount() syscall when TOMOYO or AppArmor is enabled Tetsuo Handa
2019-08-22  3:51                         ` [RFC][PATCH] fix d_absolute_path() interplay with fsmount() Al Viro
2019-08-30 10:11                           ` Tetsuo Handa
2019-07-23 21:45             ` James Morris [this message]
2019-07-23 23:30               ` [PATCH 02/10] vfs: syscall: Add move_mount(2) to move mounts around Al Viro
2019-02-19 17:08 ` [PATCH 03/10] teach move_mount(2) to work with OPEN_TREE_CLONE David Howells
2019-02-20 18:59   ` Alan Jenkins
2019-02-26 17:45   ` Alan Jenkins
2019-02-19 17:08 ` [PATCH 04/10] Make anon_inodes unconditional David Howells
2019-02-19 17:09 ` [PATCH 05/10] vfs: syscall: Add fsopen() to prepare for superblock creation David Howells
2019-02-19 17:09 ` [PATCH 06/10] vfs: Implement logging through fs_context David Howells
2019-02-19 17:09 ` [PATCH 07/10] vfs: syscall: Add fsconfig() for configuring and managing a context David Howells
2019-02-19 17:09 ` [PATCH 08/10] vfs: syscall: Add fsmount() to create a mount for a superblock David Howells
2019-02-19 17:09 ` [PATCH 09/10] vfs: syscall: Add fspick() to select a superblock for reconfiguration David Howells
2019-02-19 17:09 ` [PATCH 10/10] vfs: Add a sample program for the new mount API David Howells

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