From: Kees Cook <keescook@chromium.org>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
airlied@linux.ie, daniel@ffwll.ch, torvalds@linux-foundation.org,
akpm@linux-foundation.org, hpa@zytor.com,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
Russell King <linux@armlinux.org.uk>,
Christian Borntraeger <borntraeger@de.ibm.com>
Subject: Re: [PATCH RESEND 1/4] uaccess: Add user_read_access_begin/end and user_write_access_begin/end
Date: Thu, 2 Apr 2020 10:38:32 -0700 [thread overview]
Message-ID: <202004021035.573BBBE9AA@keescook> (raw)
In-Reply-To: <67e21b65-0e2d-7ca5-7518-cec1b7abc46c@c-s.fr>
On Thu, Apr 02, 2020 at 07:03:28PM +0200, Christophe Leroy wrote:
> > What should we do about arm and s390? There we want a cookie passed
> > from beginning of block to its end; should that be a return value?
>
> That was the way I implemented it in January, see
> https://patchwork.ozlabs.org/patch/1227926/
>
> There was some discussion around that and most noticeable was:
>
> H. Peter (hpa) said about it: "I have *deep* concern with carrying state in
> a "key" variable: it's a direct attack vector for a crowbar attack,
> especially since it is by definition live inside a user access region."
I share this concern -- we want to keep user/kernel access as static as
possible. It should be provable with static analysis, etc (e.g. objtool
does this already for x86).
Since this doesn't disrupt existing R+W access, I'd prefer the design of
this series as-is.
--
Kees Cook
next prev parent reply other threads:[~2020-04-02 17:38 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 7:34 Christophe Leroy
2020-04-02 7:34 ` [PATCH RESEND 2/4] uaccess: Selectively open read or write user access Christophe Leroy
2020-04-02 7:51 ` Kees Cook
2020-04-02 8:00 ` Christophe Leroy
2020-04-02 7:34 ` [PATCH RESEND 3/4] drm/i915/gem: Replace user_access_begin by user_write_access_begin Christophe Leroy
2020-04-02 7:52 ` Kees Cook
2020-04-02 7:59 ` Christophe Leroy
2020-04-02 7:34 ` [PATCH RESEND 4/4] powerpc/uaccess: Implement user_read_access_begin and user_write_access_begin Christophe Leroy
2020-04-02 7:52 ` Kees Cook
2020-04-02 7:46 ` [PATCH RESEND 1/4] uaccess: Add user_read_access_begin/end and user_write_access_begin/end Kees Cook
2020-04-02 16:29 ` Al Viro
2020-04-02 17:03 ` Christophe Leroy
2020-04-02 17:38 ` Kees Cook [this message]
2020-04-02 17:50 ` Al Viro
2020-04-02 18:35 ` Christophe Leroy
2020-04-02 18:35 ` Kees Cook
2020-04-02 19:26 ` Linus Torvalds
2020-04-02 20:27 ` Kees Cook
2020-04-02 20:47 ` Linus Torvalds
2020-04-03 0:58 ` Al Viro
2020-04-03 9:49 ` Russell King - ARM Linux admin
2020-04-03 11:26 ` Catalin Marinas
2020-04-03 13:37 ` Russell King - ARM Linux admin
2020-04-03 17:26 ` Al Viro
2020-04-03 10:02 ` Russell King - ARM Linux admin
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