Re: fs: sandboxed process brings host down

From	Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups	linux.kernel
Subject	Re: fs: sandboxed process brings host down
Date	2016-01-22 22:30 +0100
Message-ID	<qTRrk-1iu-1@gated-at.bofh.it> (permalink)
References	<qTR7Y-19M-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, Jan 22, 2016 at 10:06:14PM +0100, Dmitry Vyukov wrote:
> Hello,
> 
> While running syzkaller fuzzer I hit the following problem. Supervisor
> process sandboxes worker processes that do random activities with
> CLONE_NEWUSER | CLONE_NEWNS | CLONE_NEWPID | CLONE_NEWUTS |
> CLONE_NEWNET | CLONE_NEWIPC | CLONE_IO, setrlimit, chroot, etc.
> Because of that worker process gains ability to bring whole machine
> down (does not happen without the sandbox).

AFAICS, what you are doing is essentially mount --rbind / / in infinite
loop in luserns.  Which ends up eating all memory.  There's any number
of ways to do the same.  We can play whack-a-mole with them until the
kernel is completely ossified with accounting code of different sorts.
Or one can disable userns and be done with that.

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Re: fs: sandboxed process brings host down Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-22 22:30 +0100
  Re: fs: sandboxed process brings host down Dmitry Vyukov <dvyukov@google.com> - 2016-01-22 22:40 +0100
    Re: fs: sandboxed process brings host down Al Viro <viro@ZenIV.linux.org.uk> - 2016-01-22 23:00 +0100
      Re: fs: sandboxed process brings host down Robert Święcki <robert@swiecki.net> - 2016-01-22 23:40 +0100
  Re: fs: sandboxed process brings host down Kees Cook <keescook@google.com> - 2016-01-22 22:50 +0100

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