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Date: Mon, 27 Oct 2014 10:56:26 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Rik van Riel <riel@redhat.com>, David Rientjes <rientjes@google.com>,
        Aaron Tomlin <atomlin@redhat.com>, Dario Faggioli <raistlin@linux.it>,
        Andi Kleen <ak@linux.intel.com>, Peter Zijlstra <peterz@infradead.org>,
        Jens Axboe <axboe@fb.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Paul Wise <pabs3@bonedaddy.net>
Subject: Re: [PATCH] sysctl: terminate strings also on \r
Message-ID: <20141027095626.GD9807@amd>
References: <20141021202137.GA20114@www.outflux.net>
 <20141022162638.875681da6bbb9e027d2d3bee@linux-foundation.org>
 <CAGXu5j+sW89tZDA5GQnkL4E9wHTScftyxUhyAjbWnEfxGocBjg@mail.gmail.com>
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On Wed 2014-10-22 16:43:10, Kees Cook wrote:
> On Wed, Oct 22, 2014 at 4:26 PM, Andrew Morton
> <akpm@linux-foundation.org> wrote:
> > On Tue, 21 Oct 2014 13:21:37 -0700 Kees Cook <keescook@chromium.org> wrote:
> >
> >> From: Paul Wise <pabs3@bonedaddy.net>
> >>
> >> This partially mitigates a common strategy used by attackers for hiding
> >> the full contents of strings in procfs from naive sysadmins who use cat,
> >> more or sysctl to inspect the contents of strings in procfs.
> >>
> >> ...
> >>
> >> --- a/kernel/sysctl.c
> >> +++ b/kernel/sysctl.c
> >> @@ -1739,7 +1739,7 @@ static int _proc_do_string(char *data, int maxlen, int write,
> >>               while ((p - buffer) < *lenp && len < maxlen - 1) {
> >>                       if (get_user(c, p++))
> >>                               return -EFAULT;
> >> -                     if (c == 0 || c == '\n')
> >> +                     if (c == 0 || c == '\n' || c == '\r')
> >>                               break;
> >>                       data[len++] = c;
> >>               }
> >
> > There are no valid uses of \r in a procfs write?
> 
> I struggle to imagine one; everything I found that uses proc_dostring
> seems to be names, paths, and commands.

Well, filename can contain \r, right?
									Pavel
-- 
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