From: Matthew Wilcox <willy@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@infradead.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2] usercopy: Avoid HIGHMEM pfn warning
Date: Tue, 17 Sep 2019 14:32:20 -0700 [thread overview]
Message-ID: <20190917213220.GV29434@bombadil.infradead.org> (raw)
In-Reply-To: <201909171056.7F2FFD17@keescook>
On Tue, Sep 17, 2019 at 11:00:25AM -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:
>
> Now we can fetch the correct page to avoid the pfn check. In both cases,
> hardened usercopy will need to walk the page-span checker (if enabled)
> to do sanity checking.
>
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Tested-by: Randy Dunlap <rdunlap@infradead.org>
> Fixes: f5509cc18daa ("mm: Hardened usercopy")
> Cc: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
I want to make virt_to_page() do the right thing for kmapped pages,
but that is completely outside the scope of this patch.
prev parent reply other threads:[~2019-09-17 21:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-17 18:00 Kees Cook
2019-09-17 21:32 ` Matthew Wilcox [this message]
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