From: Andrew Morton <akpm@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
linux-mm@kvack.org,
Muhammad Usama Anjum <usama.anjum@collabora.com>,
David Laight <David.Laight@aculab.com>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v3] usercopy: Check valid lifetime via stack depth
Date: Fri, 25 Feb 2022 17:46:57 -0800 [thread overview]
Message-ID: <20220225174657.9e1af8ec59ce8dbf223f84c5@linux-foundation.org> (raw)
In-Reply-To: <202202251728.1634F405@keescook>
On Fri, 25 Feb 2022 17:35:49 -0800 Kees Cook <keescook@chromium.org> wrote:
> On Fri, Feb 25, 2022 at 04:01:57PM -0800, Andrew Morton wrote:
> > On Fri, 25 Feb 2022 09:33:45 -0800 Kees Cook <keescook@chromium.org> wrote:
> >
> > > Under CONFIG_HARDENED_USERCOPY=y, when exact stack frame boundary checking
> > > is not available (i.e. everything except x86 with FRAME_POINTER), check
> > > a stack object as being at least "current depth valid", in the sense
> > > that any object within the stack region but not between start-of-stack
> > > and current_stack_pointer should be considered unavailable (i.e. its
> > > lifetime is from a call no longer present on the stack).
> > >
> > > Introduce ARCH_HAS_CURRENT_STACK_POINTER to track which architectures
> > > have actually implemented the common global register alias.
> > >
> > > Additionally report usercopy bounds checking failures with an offset
> > > from current_stack_pointer, which may assist with diagnosing failures.
> > >
> > > The LKDTM USERCOPY_STACK_FRAME_TO and USERCOPY_STACK_FRAME_FROM tests
> > > (once slightly adjusted in a separate patch) will pass again with
> > > this fixed.
> >
> > Again, what does this actually do?
>
> [answers]
>
OK, thanks. I think a new changelog is warranted?
What's your preferred path for upstreaming this change?
next prev parent reply other threads:[~2022-02-26 1:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-25 17:33 Kees Cook
2022-02-26 0:01 ` Andrew Morton
2022-02-26 1:35 ` Kees Cook
2022-02-26 1:46 ` Andrew Morton [this message]
2022-02-26 2:22 ` Kees Cook
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