Re: [RCF] [PATCH] unprivileged mount/umount

From: Ram (linuxram_at_us.ibm.com)
Date: 05/12/05

  • Next message: Joe Seigh: "Re: RCU + SMR for preemptive kernel/user threads." 
    To: Jamie Lokier <jamie@shareable.org>
Date:	Wed, 11 May 2005 15:42:13 -0700

    On Wed, 2005-05-11 at 14:28, Jamie Lokier wrote:
    > Ram wrote:
    > > What if proc filesystem is removed from the kernel?
    > >
    > > Ability to access some other namespace through the proc filesystem does
    > > not look clean. I think it should be cleanly supported through VFS.
    >
    > You don't have to use /proc/NNN/root - that's just one convenient way
    > to do it.
    >
    > Other ways are
    >
    > run_in_namespace mount -t bind / /var/namespaces/$NAME
    >
    > and
    >
    > clone + open("/") + pass to parent using unix socket
    >
    > which I think both work already.
    >
    > > Also cd'ing into a new namespace just allows you to browse through
    > > the other namespace. But it does not effectively change the process's
    > > namespace. Things like mount in the other namespace will be failed
    > > by check_mount() anyway.
    >
    > That's correct.
    >
    > > I think, we need sys calls like sys_cdnamespace() which switches to a
    > > new namespace.
    >
    > Can you give a reason why sys_chdir() shouldn't have that behaviour?

    Do you mean to say you want to change the namespace when a process
    changes to a directory which belongs to that namespace?

    Well it makes it totally confusing. A user would start seeing different
    set of mounts suddenly as he changes directories beloning to different
    namespaces. I am not sure, if changing namespace implicitly is a good
    idea. Not saying its a bad idea, but seems to change my notion of
    namespaces completely.

    I think a process should have access to one
    namespace at any given point in time, and should have the ability
    to explicitly switch to a different namespace of its choice, provided
    it has enough access permission to that namespace.

    having the ability to access two namespaces simultaneously can allow
    cross contamination. Which essentially makes namespaces as a concept
    irrelevent.

    RP

    >
    > > Effectively the process's current->namespace has to be modified,
    > > for the process to be effectively work in the new namespace.
    >
    > Or just remove current->namespace. It's entire purpose seems to be to
    > prevent namespaces from being first class objects. The idea of
    > "current namespace" is adequately represented by
    > current->fs->mnt_root->mnt_namespace IMHO.
    >
    > -- Jamie

    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

  • Next message: Joe Seigh: "Re: RCU + SMR for preemptive kernel/user threads."

    Relevant Pages

    • Re: [PATCH] private mounts
      ... What if some filesystem allowed access to vfsmount in other namespace? ... Just like the proc filesystem having the ability to do so, ... send the line "unsubscribe linux-kernel" in ...
      (Linux-Kernel)
    • Re: TIP 278: does it cause any breakage?
      ... namespace, and it should work the same as it does for procedures. ... we bring them into our current scope. ... never found a use for 's ability to set the value, ... I'd love to see [upvar] get the ability to take a namespace instead of ...
      (comp.lang.tcl)
    • Re: [RCF] [PATCH] unprivileged mount/umount
      ... Ability to access some other namespace through the proc filesystem does ... send the line "unsubscribe linux-kernel" in ...
      (Linux-Kernel)
    • Re: [RCF] [PATCH] unprivileged mount/umount
      ... > Ability to access some other namespace through the proc filesystem does ... Jamie's proposal was to make chroot() swich namespace. ... send the line "unsubscribe linux-kernel" in ...
      (Linux-Kernel)
    • Re: [RCF] [PATCH] unprivileged mount/umount
      ... > Ability to access some other namespace through the proc filesystem does ... But it does not effectively change the process's ... send the line "unsubscribe linux-kernel" in ...
      (Linux-Kernel)
    Loading