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Date:   Thu, 10 Oct 2019 09:43:26 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Aleksa Sarai <cyphar@cyphar.com>
Cc:     Michael Ellerman <mpe@ellerman.id.au>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Christian Brauner <christian@brauner.io>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        libc-alpha@sourceware.org, linux-api@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/4] lib: introduce copy_struct_from_user() helper
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On Thu, Oct 10, 2019 at 10:40:07PM +1100, Aleksa Sarai wrote:
> Yeah, it takes about 5-10s on my laptop. We could switch it to just
> everything within a 4K block, but the main reason for testing with
> 2*PAGE_SIZE is to make sure that check_nonzero_user() works across page
> boundaries. Though we could only do check_nonzero_user() in the region
> of the page boundary (maybe i E (PAGE_SIZE-512,PAGE_SIZE+512]?)

Yeah, I like this idea: just poke at the specific edge-case.

-- 
Kees Cook