linux-kernel - Re: [PATCH] usercopy: Skip HIGHMEM page checking

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Message-ID: <201909171039.09E75C2@keescook>
Date:   Tue, 17 Sep 2019 10:39:50 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH] usercopy: Skip HIGHMEM page checking

On Tue, Sep 17, 2019 at 09:36:06AM -0700, Matthew Wilcox wrote:
> If the copy has the correct bounds, the 'wholly within one base page'
> check will pass and it'll return.  If the copy does span a page,
> the virt_to_head_page(end) call will return something bogus, then the
> PageReserved and CMA test will cause the usercopy_abort() test to fail.
> 
> So I think your first patch is the right patch.

Okay, good points. I'll respin...

-- 
Kees Cook