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Date: Wed, 13 Feb 2019 13:06:01 +0400
From: Loganaden Velvindron <loganaden@...il.com>
To: oss-security@...ts.openwall.com
Cc: Solar Designer <solar@...nwall.com>, Aleksa Sarai <cyphar@...har.com>, dev@...ncontainers.org, 
	Christian Brauner <christian.brauner@...ntu.com>
Subject: Re: CVE-2019-5736: runc container breakout (all versions)

I think that someone already posted a PoC on github, AFAIK.

On Wed, Feb 13, 2019 at 1:04 PM Aleksa Sarai <asarai@...e.de> wrote:

> On 2019-02-12, Solar Designer <solar@...nwall.com> wrote:
> >  static int proc_exe_link(struct dentry *dentry, struct path *exe_path)
> >  {
> >         struct task_struct *task;
> > @@ -1628,10 +1780,15 @@ static int proc_exe_link(struct dentry *dentry,
> > struct path *exe_path)
> >         exe_file = get_task_exe_file(task);
> >         put_task_struct(task);
> >         if (exe_file) {
> > -               *exe_path = exe_file->f_path;
> > -               path_get(&exe_file->f_path);
> > +               int result;
> > +
> > +               result = path_in_ve(&exe_file->f_path);
> > +               if (result == 0) {
> > +                       *exe_path = exe_file->f_path;
> > +                       path_get(&exe_file->f_path);
> > +               }
> >                 fput(exe_file);
> > -               return 0;
> > +               return result;
> >         } else
> >                 return -ENOENT;
> >  }
> > ---
> >
> > This uses Virtuozzo/OpenVZ specific APIs, so won't be directly usable
> > elsewhere, but maybe a similar approach could be used upstream?
>
> I have just sent v5 of my AT_THIS_ROOT patchset to LKML[1] -- which
> allows userspace processes to block resolution of magic links. While
> blocking access through /proc/self/exe helps block this issues, being
> able to block (from userspace) resolution of all magic links would
> massively help avoid problems like this.
>
> [1]: https://marc.info/?l=linux-api&m=155002737629350&w=2
>
> --
> Aleksa Sarai
> Senior Software Engineer (Containers)
> SUSE Linux GmbH
> <https://www.cyphar.com/>
>

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