From: Kees Cook <keescook@chromium.org>
To: P J P <ppandit@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Josh Triplett <josh@joshtriplett.org>,
Serge Hallyn <serge.hallyn@canonical.com>,
linux-fsdevel@vger.kernel.org, halfdog <me@halfdog.net>
Subject: Re: [PATCH] exec: do not leave bprm->interp on stack
Date: Sun, 18 Nov 2012 11:34:48 -0800 [thread overview]
Message-ID: <CAGXu5jJ4ZuviFMQcFocLWfcMreZSt4kCHFNm-PNW+yuy+v+FiQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1211182211350.5012@wniryva.cad.erqung.pbz>
On Sun, Nov 18, 2012 at 11:04 AM, P J P <ppandit@redhat.com> wrote:
> +-- On Fri, 16 Nov 2012, Kees Cook wrote --+
> | Hrm? It should be showing only the live heap-allocated interp -- are
> | you seeing uninitialized contents?
>
> I don't see uninitialised content; I see interpreter names from previous
> iterations. Which was the case earlier as well. The - interp - array is
> initialised with the interpreter name, before being assigned to bprm->interp.
>
> These - interp - bytes are *leaked* because after 4 recursions, when
> load_script returns -ENOEXEC, - bprm->interp - becomes invalid for it starts
> pointing to an invalid stack memory location.
>
> Crux of the problem is in the fact that the recursion limit -
> BINPRM_MAX_RECURSION(4) - exceeds after ones been rightly adhered to.
>
> (bprm->recursion_depth > BINPRM_MAX_RECURSION))
> return -ENOEXEC;
>
> This check fails due to specific condition, which still exists.
>
> Dynamically allocating memory fixes the leak by making the memory area live
> and valid.
Right. There are two problems. This fixes the first, which is the
memory content leak.
> It does not fix the problem which caused the leak in the first place by
> exceeding the BINPRM_MAX_RECURSION, not by 1 or 2 but possible 2^6
> recursions. Isn't that performance hit?
This is the second problem. I view this as less critical because it's
only 64 instead of 4, but it certainly should be solved as well.
-Kees
--
Kees Cook
Chrome OS Security
next prev parent reply other threads:[~2012-11-18 19:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-24 23:20 [PATCH] exec: do not leave bprm->interp on stack Kees Cook
2012-10-25 4:16 ` Al Viro
2012-10-25 6:21 ` Kees Cook
2012-10-25 11:46 ` P J P
2012-10-25 12:03 ` Tetsuo Handa
2012-10-25 12:57 ` P J P
2012-10-25 12:09 ` Al Viro
2012-10-25 12:38 ` Al Viro
2012-10-26 17:38 ` P J P
2012-10-26 18:36 ` Al Viro
2012-10-27 10:47 ` P J P
2012-10-27 17:05 ` Kees Cook
2012-10-27 20:16 ` P J P
2012-10-28 3:32 ` Kees Cook
2012-11-06 8:10 ` P J P
2012-11-12 22:10 ` Kees Cook
2012-11-13 6:50 ` halfdog
2012-11-16 12:50 ` P J P
2012-11-16 18:00 ` Kees Cook
2012-11-18 19:04 ` P J P
2012-11-18 19:34 ` Kees Cook [this message]
2012-11-19 6:57 ` P J P
2012-11-19 20:41 ` Kees Cook
2012-11-20 7:04 ` P J P
2012-11-22 20:06 ` P J P
2012-11-23 18:43 ` P J P
2012-11-23 23:12 ` Tetsuo Handa
[not found] ` <alpine.LFD.2.02.1211221934220.19768@wniryva.cad.erqung.pbz>
[not found] ` <CAGXu5jL8zCt5ghW4ODPL9+SyC9+mbuw=4JMUngepY5fC8pSikQ@mail.gmail.com>
2012-11-26 7:09 ` P J P
[not found] ` <CA+55aFx3LFH5Xj1OkNoy7vN5w8y5tH39MUDujKqF3BdnmYibLQ@mail.gmail.com>
2012-11-20 7:08 ` P J P
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