Messages in this thread | | | Date | Thu, 26 Feb 2009 00:16:45 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/2] exit_notify: kill the wrong capable(CAP_KILL) check |
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On 02/25, Serge E. Hallyn wrote: > > Quoting Oleg Nesterov (oleg@redhat.com): > > On 02/25, Serge E. Hallyn wrote: > > > > > > Quoting Oleg Nesterov (oleg@redhat.com): > > > > On 02/25, Serge E. Hallyn wrote: > > > > 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. > > > > I think you misread this CAP_KILL check. > > > > It does not restrict the unprivileged task to send the signal. Instead, > > if the exiting task has CAP_KILL, we bypass other security checks. > > ? If the exiting task does not have CAP_KILL,
_and_ (not "or") the execution domains for parent/chils are different,
> we set the signal to > SIGCHILD (which is deemed safe).
Yes. So why we should not set the signal to SIGCHLD if the task has CAP_KILL ?
And again, the malicious application can exec the setuid binary before exit, in this case we never reset ->exit_signal (of course, unless that binary drops CAP_KILL).
Oleg.
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