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From: Matthew Wilcox <willy@infradead.org>
To: David Hildenbrand <david@redhat.com>
Cc: Kees Cook <keescook@chromium.org>,
	linux-mm@kvack.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH 4/4] usercopy: Remove HARDENED_USERCOPY_PAGESPAN
Date: Mon, 31 Jan 2022 19:27:35 +0000	[thread overview]
Message-ID: <Yfg4J63vdl8S0pG2@casper.infradead.org> (raw)
In-Reply-To: <2858cfa9-2329-6da9-82b8-643f29d548e6@redhat.com>

On Mon, Jan 31, 2022 at 03:27:02PM +0100, David Hildenbrand wrote:
> On 11.01.22 00:15, Matthew Wilcox (Oracle) wrote:
> > There isn't enough information to make this a useful check any more;
> > the useful parts of it were moved in earlier patches, so remove this
> > set of checks now.
> > 
> > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> 
> 
> Very nice cleanup IMHO
> 
> Reviewed-by: David Hildenbrand <david@redhat.com>

Thanks.  I'm thinking about adding another check.  If the order-0
page has a non-NULL ->mapping, I believe that is enough to determine
that it's a page cache / KSM / Anon page, and as such is guaranteed
to actually be order-0 (and not part of a postive-order allocation
without __GFP_COMP set).  But that would require a bit more auditing,
or just throwing it in and seeing what breaks *whistles*.

      reply	other threads:[~2022-01-31 19:27 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-10 23:15 [PATCH 0/4] Assorted improvements to usercopy Matthew Wilcox (Oracle)
2022-01-10 23:15 ` [PATCH 1/4] mm/usercopy: Check kmap addresses properly Matthew Wilcox (Oracle)
2022-05-10  3:37   ` Andrew Morton
2022-05-10 22:01     ` Kees Cook
2022-01-10 23:15 ` [PATCH 2/4] mm/usercopy: Detect vmalloc overruns Matthew Wilcox (Oracle)
2022-01-10 23:15 ` [PATCH 3/4] mm/usercopy: Detect large folio overruns Matthew Wilcox (Oracle)
2022-01-31 14:28   ` David Hildenbrand
2022-01-10 23:15 ` [PATCH 4/4] usercopy: Remove HARDENED_USERCOPY_PAGESPAN Matthew Wilcox (Oracle)
2022-01-12 23:08   ` Kees Cook
2022-01-31 14:27   ` David Hildenbrand
2022-01-31 19:27     ` Matthew Wilcox [this message]

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