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 16:01:57 -0800 [thread overview]
Message-ID: <20220225160157.680ecdea21ce81183059bb63@linux-foundation.org> (raw)
In-Reply-To: <20220225173345.3358109-1-keescook@chromium.org>
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?
> Reported-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
A link to that report would shed some light. But actually describing
the user-visible impact right there in the changelog is preferable.
It sounds like a selftest is newly failing, which makes it a
userspace-visible regression, perhaps?
If so, do we have a Fixes: and is a cc:stable warranted?
next prev parent reply other threads:[~2022-02-26 0:02 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 [this message]
2022-02-26 1:35 ` Kees Cook
2022-02-26 1:46 ` Andrew Morton
2022-02-26 2:22 ` Kees Cook
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