Re: [PATCH v3] vfs: new O_NODE open flag

From: Miklos Szeredi
Date: Wed Dec 02 2009 - 15:14:28 EST

On Wed, 2 Dec 2009, Alan Cox wrote:
> > 1) There's a security hole with dynamicly allocated devices if
> > permissions on new device are difference than on old device.
> >
> > The issue is valid, but also exists if hard links are created to
> > device nodes. udev already defends against this by setting
> > permissions on device to zero before unlinking it.
> udev defends against it with the specific knowledge that any existing
> open means the device is open and cannot be unloaded. The combination is
> required (and some other happenstance properties).

You're still missing the point. O_NODE is like a hard link, except
the reference doesn't come from the filesystem but from a file
descriptor. From udev's perspective there's no difference.

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