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From: ebiederm@xmission.com (Eric W. Biederman)
To: Seth Forshee <seth.forshee@canonical.com>
Cc: Linux Containers <containers@lists.linux-foundation.org>,
	linux-fsdevel@vger.kernel.org,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Christian Brauner <christian@brauner.io>,
	linux-kernel@vger.kernel.org
Subject: Re: [REVIEW][PATCH 2/6] vfs: Allow userns root to call mknod on owned filesystems.
Date: Thu, 24 May 2018 11:55:45 -0500	[thread overview]
Message-ID: <87y3g92dta.fsf@xmission.com> (raw)
In-Reply-To: <20180524135517.GQ3401@ubuntu-xps13> (Seth Forshee's message of "Thu, 24 May 2018 08:55:17 -0500")

Seth Forshee <seth.forshee@canonical.com> writes:

> On Wed, May 23, 2018 at 06:25:34PM -0500, Eric W. Biederman wrote:
>> These filesystems already always set SB_I_NODEV so mknod will not be
>> useful for gaining control of any devices no matter their permissions.
>> This will allow overlayfs and applications to fakeroot to use device
>> nodes to represent things on disk.
>> 
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>
> For a normal filesystem this does seem safe enough.
>
> However, I'd also like to see us allow unprivileged mounting for
> overlayfs, and there we need to worry about whether this would allow a
> mknod in an underlying filesystem which should not be allowed. That
> mknod will be subject to this same check in the underlying filesystem
> using the credentials of the user that mounted the overaly fs, which
> should be sufficient to ensure that the mknod is permitted.

Sufficient to ensure the mknod is not permitted on the underlying
filesystem.  I believe you mean.

> Thus this looks okay to me.
>
> Acked-by: Seth Forshee <seth.forshee@canonical.com>

Eric

  reply	other threads:[~2018-05-24 16:56 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-23 23:22 [REVIEW][PATCH 0/6] Wrapping up the vfs support for unprivileged mounts Eric W. Biederman
2018-05-23 23:25 ` [REVIEW][PATCH 1/6] vfs: Don't allow changing the link count of an inode with an invalid uid or gid Eric W. Biederman
2018-05-24 12:58   ` Seth Forshee
2018-05-24 22:30     ` Christian Brauner
     [not found]   ` <20180523232538.4880-1-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-24 12:58     ` Seth Forshee
2018-05-23 23:25 ` [REVIEW][PATCH 2/6] vfs: Allow userns root to call mknod on owned filesystems Eric W. Biederman
     [not found]   ` <20180523232538.4880-2-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-24 13:55     ` Seth Forshee
2018-05-24 13:55   ` Seth Forshee
2018-05-24 16:55     ` Eric W. Biederman [this message]
     [not found]       ` <87y3g92dta.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-24 17:22         ` Seth Forshee
2018-05-24 17:22           ` Seth Forshee
2018-05-24 16:55     ` Eric W. Biederman
2018-05-24 19:12   ` Christian Brauner
2018-05-23 23:25 ` [REVIEW][PATCH 3/6] fs: Allow superblock owner to replace invalid owners of inodes Eric W. Biederman
2018-05-23 23:41   ` [REVIEW][PATCH v2 " Eric W. Biederman
2018-05-24 22:30     ` Christian Brauner
     [not found]   ` <20180523232538.4880-3-ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-23 23:41     ` Eric W. Biederman
     [not found] ` <87o9h6554f.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-23 23:25   ` [REVIEW][PATCH 1/6] vfs: Don't allow changing the link count of an inode with an invalid uid or gid Eric W. Biederman
2018-05-23 23:25   ` [REVIEW][PATCH 2/6] vfs: Allow userns root to call mknod on owned filesystems Eric W. Biederman
2018-05-23 23:25   ` [REVIEW][PATCH 3/6] fs: Allow superblock owner to replace invalid owners of inodes Eric W. Biederman
2018-05-23 23:25   ` [REVIEW][PATCH 4/6] fs: Allow superblock owner to access do_remount_sb() Eric W. Biederman
2018-05-23 23:25   ` [REVIEW][PATCH 5/6] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Eric W. Biederman
2018-05-23 23:25   ` [REVIEW][PATCH 6/6] fs: Allow CAP_SYS_ADMIN in s_user_ns to freeze and thaw filesystems Eric W. Biederman
2018-05-24 21:46   ` [REVIEW][PATCH 0/6] Wrapping up the vfs support for unprivileged mounts Theodore Y. Ts'o
2018-05-29 15:40   ` Dongsu Park
2018-05-23 23:25 ` [REVIEW][PATCH 4/6] fs: Allow superblock owner to access do_remount_sb() Eric W. Biederman
2018-05-24 15:58   ` Christian Brauner
     [not found]     ` <20180524155803.GB19932-cl+VPiYnx/1AfugRpC6u6w@public.gmane.org>
2018-05-24 16:45       ` Eric W. Biederman
2018-05-24 16:45     ` Eric W. Biederman
2018-05-24 17:28       ` Christian Brauner
2018-05-23 23:25 ` [REVIEW][PATCH 5/6] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Eric W. Biederman
2018-05-24 15:57   ` Christian Brauner
2018-05-23 23:25 ` [REVIEW][PATCH 6/6] fs: Allow CAP_SYS_ADMIN in s_user_ns to freeze and thaw filesystems Eric W. Biederman
2018-05-24 15:59   ` Christian Brauner
2018-05-24 21:46 ` [REVIEW][PATCH 0/6] Wrapping up the vfs support for unprivileged mounts Theodore Y. Ts'o
2018-05-24 23:23   ` Eric W. Biederman
2018-05-25  3:57     ` Dave Chinner
2018-05-25  4:06       ` Darrick J. Wong
2018-05-25  4:06         ` Darrick J. Wong
2018-05-29 13:12       ` Eric W. Biederman
2018-05-29 13:12       ` Eric W. Biederman
2018-05-29 22:17         ` Dave Chinner
2018-05-30  2:34           ` Eric W. Biederman
2018-05-30  2:34             ` Eric W. Biederman
2018-05-30  4:34             ` Dave Chinner
     [not found]             ` <87k1rlkh1g.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-30  4:34               ` Dave Chinner
     [not found]         ` <8736yar4g3.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-29 22:17           ` Dave Chinner
     [not found]     ` <87y3g8y6x9.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
2018-05-25  3:57       ` Dave Chinner
     [not found]   ` <20180524214617.GG7712-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2018-05-24 23:23     ` Eric W. Biederman
2018-05-29 15:40 ` Dongsu Park

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