netdev - Re: [PATCH 6/8] scm: Capture the full credentials of the scm sender.

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Message-ID: <20100616044719.GA23863@hallyn.com>
Date:	Tue, 15 Jun 2010 23:47:19 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Containers <containers@...ts.osdl.org>,
	Serge Hallyn <serue@...ibm.com>,
	Pavel Emelyanov <xemul@...allels.com>, netdev@...r.kernel.org
Subject: Re: [PATCH 6/8] scm: Capture the full credentials of the scm
 sender.

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> "Serge E. Hallyn" <serge@...lyn.com> writes:
> > I think this hunk needs to be documented.  I.e. given that scm_send()
> > will call scm_set_cred() before calling __scm_send, I don't see how
> > these conditions could happen?  If the condition can legitimately
> > happen, then given all of the pid_t vs struct pid and 'cred' vs. 'creds'
> > in these two hunks, I think a comment over each would be nice.
> 
> I think if you have the full context of __scm_send it becomes pretty obvious.
> 
> 		case SCM_CREDENTIALS:
> 			if (cmsg->cmsg_len != CMSG_LEN(sizeof(struct ucred)))
> 				goto error;
> 			memcpy(&p->creds, CMSG_DATA(cmsg), sizeof(struct ucred));
> 			err = scm_check_creds(&p->creds);
> 			if (err)
> 				goto error;
> 
> At this point we have just copied ucred from userspace.  We have done
> scm_check_creds to ensure we allow the user to send the pid, uid, and
> gid they have passed in.
> 
> These tests catch the case where the user is legitimately sending
> something other than their own credentials.

Of course.  Sorry.  And I even had the context in the window next to the
email...  So finally,

Acked-by: Serge E. Hallyn <serge@...lyn.com>

to the set, and I'm looking forward to this being in.  And it should solve
the nuisance of containers without private netns rebooting their hosts
when both use upstart.

thanks,
-serge
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