From: "Serge E. Hallyn" <serge@hallyn.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Chris Evans <scarybeasts@gmail.com>,
David Howells <dhowells@redhat.com>,
Don Howard <dhoward@redhat.com>, Eugene Teo <eugene@redhat.com>,
Michael Kerrisk <mtk.manpages@googlemail.com>,
Tavis Ormandy <taviso@sdf.lonestar.org>,
Vitaly Mayatskikh <vmayatsk@redhat.com>,
stable@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] exit_notify: kill the wrong capable(CAP_KILL) check
Date: Wed, 25 Feb 2009 16:14:15 -0600 [thread overview]
Message-ID: <20090225221415.GA1751@hallyn.com> (raw)
In-Reply-To: <20090225220324.GA14667@redhat.com>
Quoting Oleg Nesterov (oleg@redhat.com):
> On 02/25, Serge E. Hallyn wrote:
> >
> > Quoting Roland McGrath (roland@redhat.com):
> > > > I can't understand why exit_notify() checks capable(CAP_KILL), but this
> > > > looks just wrong.
> > >
> > > I don't know either why it's there. My guess is that it was not actually
> > > thought out specifically, just a "unless capable" exception added when the
> > > security-motivated exclusions (exec_id stuff) were added.
> > >
> > > I can't think of any reason not to drop this check.
> >
> > Because of the following test?
> >
> > #include <stdio.h>
> > #include <sched.h>
> > #include <signal.h>
> > #include <stdlib.h>
> >
> > int childfn(void *data)
> > {
> > printf("hi there, i'm the child\n");
> > sleep(10);
> > exit(0);
> > }
> >
> > int main()
> > {
> > int stacksize = 4*getpagesize();
> > void *stack, *stacktop;
> >
> > stack = malloc(stacksize);
> > stacktop = stack + stacksize;
> >
> > int p = clone(childfn, stacktop, CLONE_PARENT|SIGSTOP, NULL);
> > exit(0);
> > }
>
> Can't understand... Why do you think CAP_KILL makes things better?
>
> Actually, how can it make any difference in this case?
Well the check by itself isn't quite right - it seems to me it
should also check whether tsk->euid == parent->uid. But letting
an unprivileged task send SIGSTOP to a privileged one bc of
some fluke in the task hierarchy doesn't seem right.
-serge
next prev parent reply other threads:[~2009-02-25 22:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-25 19:02 [PATCH 2/2] exit_notify: kill the wrong capable(CAP_KILL) check Oleg Nesterov
2009-02-25 19:41 ` Roland McGrath
2009-02-25 21:53 ` Serge E. Hallyn
2009-02-25 22:03 ` Oleg Nesterov
2009-02-25 22:14 ` Serge E. Hallyn [this message]
2009-02-25 22:32 ` Oleg Nesterov
2009-02-25 22:47 ` Serge E. Hallyn
2009-02-25 23:16 ` Oleg Nesterov
2009-02-25 23:54 ` Serge E. Hallyn
2009-04-06 14:16 ` [PATCH, RESEND] " Oleg Nesterov
2009-04-06 19:36 ` Roland McGrath
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