linux-kernel - Re: [PATCH] ptrace: use fsuid, fsgid, effective creds for fs access checks

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Message-ID: <20151207203824.GA27364@pc.thejh.net>
Date:	Mon, 7 Dec 2015 21:38:24 +0100
From:	Jann Horn <jann@...jh.net>
To:	Kees Cook <keescook@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Joe Perches <joe@...ches.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	linux-security-module <linux-security-module@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	"security@...nel.org" <security@...nel.org>,
	Willy Tarreau <w@....eu>
Subject: Re: [PATCH] ptrace: use fsuid, fsgid, effective creds for fs access
 checks

On Mon, Dec 07, 2015 at 12:32:06PM -0800, Kees Cook wrote:
> On Sat, Dec 5, 2015 at 6:04 PM, Jann Horn <jann@...jh.net> wrote:
[...]
> > -       if (ptrace_may_access(task, PTRACE_MODE_READ)) {
> > +       if (ptrace_may_access(task, PTRACE_MODE_READ | PTRACE_MODE_FSCREDS)) {
> 
> This should maybe use the PTRACE_MODE_READ_FSCREDS macro?

Oh, yes. I don't know how I missed that. :/


> >                 error = ns_get_path(&ns_path, task, ns_ops);
> >                 if (!error)
> >                         nd_jump_link(&ns_path);
> > @@ -63,7 +63,7 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
> >         if (!task)
> >                 return res;
> >
> > -       if (ptrace_may_access(task, PTRACE_MODE_READ)) {
> > +       if (ptrace_may_access(task, PTRACE_MODE_READ | PTRACE_MODE_FSCREDS)) {
> 
> same here?

Yes.
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