Messages in this thread | | | From | (Eric W. Biederman) | Date | Mon, 15 Oct 2018 13:07:21 -0500 | Subject | Re: [RFC] Allow user namespace inside chroot |
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Jann Horn <jannh@google.com> writes:
> On Mon, Oct 15, 2018 at 7:10 PM <nagarathnam.muthusamy@oracle.com> wrote: >> @@ -1281,7 +1285,7 @@ static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns) >> return -ENOMEM; >> >> put_user_ns(cred->user_ns); >> - set_cred_user_ns(cred, get_user_ns(user_ns)); >> + set_cred_user_ns(cred, get_user_ns(user_ns), 0); > > This looks bogus. With this, I think your restriction can be bypassed > if process A forks a child B, B creates a new user namespace, then A > enters the user namespace with setns() and has full capabilities. Am I > missing something?
Nope. I feel silly for missing that angle.
Even without the full capabilities the userns_install angle will place you at the root of the mount namespace outside of the chroot.
At which point I have visions of the special cases multiplying like bunnies make this work. Without a very strong case I don't like this at all.
Eric
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