Re: [RFC] FUSE permission modell (Was: fuse review bits)

["Bodo Eggert <harvested.in.lkml@posting.7eggert.dyndns.org>" <7eggert@gmx.de>]

Mike Waychison <mike@waychison.com> wrote:

> Consider the following pseudo example:
> 
> main():
> chdir("/");
> fd = open(".", O_RDONLY);
> clone(cloned_func, cloned_stack, CLONE_NEWNS, NULL);
> 
> cloned_func:
> fchdir(fd);
> chdir("..");
> 
> if main is run within a chroot where it's "/" is on the same vfsmount as
>  it's "..", then the application can step out of the chroot using clone(2).
> 
> Note: using chdir in a vfsmount outside of your namespace works, however
> you won't be able to walk off that vfsmount (to its parent or children).

IMO the '..' file descriptor should be attached to it's chroot domain.
This should avoid all chroot-escapes, even with fd-passing etc.

I wonder why nobody thought of that. Either it's too obvious or too stupid.
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