Messages in this thread | | | From | Andy Lutomirski <> | Date | Thu, 17 Sep 2015 15:15:53 -0700 | Subject | Re: [PATCH v3 2/7] userns: Simpilify MNT_NODEV handling. |
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On Sep 16, 2015 6:01 PM, "Eric W. Biederman" <ebiederm@xmission.com> wrote: > > Andy Lutomirski <luto@amacapital.net> writes: > > > On Wed, Sep 16, 2015 at 1:02 PM, Seth Forshee > > <seth.forshee@canonical.com> wrote: > >> From: "Eric W. Biederman" <ebiederm@xmission.com> > >> > >> - Consolidate the testing if a device node may be opened in a new > >> function may_open_dev. > >> > >> - Move the check for allowing access to device nodes on filesystems > >> not mounted in the initial user namespace from mount time to open > >> time and include it in may_open_dev. > >> > >> This set of changes removes the implicit adding of MNT_NODEV which > >> simplifies the logic in fs/namespace.c and removes a potentially > >> problematic user visible difference in how normal and unprivileged > >> mount namespaces work. > >> > >> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> > > > >> - /* Only in special cases allow devices from mounts > >> - * created outside the initial user namespace. > >> - */ > >> - if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) { > >> - flags |= MS_NODEV; > >> - mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV; > >> - } > > > > This is an ABI change. It's probably okay, but I think the commit > > message should make it clear what's happening. > > You mean it should include in big flashing neon letters > ***REGRESSION FIX*** > ? > > It is longer in coming than I had hoped. But that is part of the reason > I did not fix the security hole this way. Getting the s_user_ns stuff > just so has been non-trivial. > > I do agree that because this is a user visible change we do need to keep > our eyes peeled for pieces of userspace software that may depend on the > exact details of the current behavior.
Yeah. "Removes a potentially problematic user visible difference" sounds like the difference has been there forever. If it needs to get backported, people will appreciate it.
--Andy
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