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Message-ID: <370bb00d-8c1c-1a69-7c7f-f6135b16b4fa@intel.com>
Date: Wed, 20 Sep 2017 16:25:48 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Tycho Andersen <tycho@...ker.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
kernel-hardening@...ts.openwall.com,
Marco Benatto <marco.antonio.780@...il.com>,
Juerg Haefliger <juerg.haefliger@...onical.com>,
Juerg Haefliger <juerg.haefliger@....com>
Subject: Re: [PATCH v5 03/10] swiotlb: Map the buffer if it was unmapped by
XPFO
On 09/20/2017 03:47 PM, Tycho Andersen wrote:
>
>>> static inline void *skcipher_map(struct scatter_walk *walk)
>>> {
>>> struct page *page = scatterwalk_page(walk);
>>>
>>> return (PageHighMem(page) ? kmap_atomic(page) : page_address(page)) +
>>> offset_in_page(walk->offset);
>>> }
>> Is there any better way to catch these? Like, can we add some debugging
>> to check for XPFO pages in __va()?
> Yes, and perhaps also a debugging check in PageHighMem?
I'm not sure what PageHighMem() would check. It's OK to use as long as
you don't depend on the contents of the page.
> Would __va have caught either of the two cases you've pointed out?
Yes. __va() is what is eventually called by lowmem_page_address(),
which is only OK to call on things that are actually mapped into the kernel.
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