From: Kees Cook <keescook@chromium.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] usercopy: Skip HIGHMEM page checking
Date: Mon, 16 Sep 2019 20:05:00 -0700 [thread overview]
Message-ID: <201909162003.FEEAC65@keescook> (raw)
In-Reply-To: <20190917003209.GS29434@bombadil.infradead.org>
On Mon, Sep 16, 2019 at 05:32:09PM -0700, Matthew Wilcox wrote:
> On Mon, Sep 16, 2019 at 02:32:56PM -0700, Kees Cook wrote:
> > When running on a system with >512MB RAM with a 32-bit kernel built with:
> >
> > CONFIG_DEBUG_VIRTUAL=y
> > CONFIG_HIGHMEM=y
> > CONFIG_HARDENED_USERCOPY=y
> >
> > all execve()s will fail due to argv copying into kmap()ed pages, and on
> > usercopy checking the calls ultimately of virt_to_page() will be looking
> > for "bad" kmap (highmem) pointers due to CONFIG_DEBUG_VIRTUAL=y:
>
> I don't understand why you want to skip the check. We must not cross a
> page boundary of a kmapped page.
That requires a new test which hasn't existed before. First I need to
fix the bug, and then we can add a new test and get that into -next,
etc.
--
Kees Cook
next prev parent reply other threads:[~2019-09-17 3:05 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-16 21:32 [PATCH] usercopy: Skip HIGHMEM page checking Kees Cook
2019-09-17 0:32 ` Matthew Wilcox
2019-09-17 3:05 ` Kees Cook [this message]
2019-09-17 16:36 ` Matthew Wilcox
2019-09-17 17:39 ` Kees Cook
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