linux-kernel - Re: [PATCH v2] mm: unexport globally copy_to_kernel

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Message-ID: <aac5662d-b764-426c-a763-79053ecea1a5@redhat.com>
Date: Mon, 23 Jun 2025 10:09:43 +0200
From: David Hildenbrand <david@...hat.com>
To: Sabyrzhan Tasbolatov <snovitoll@...il.com>, andreyknvl@...il.com
Cc: akpm@...ux-foundation.org, arnd@...db.de, dvyukov@...gle.com,
 elver@...gle.com, glider@...gle.com, hch@...radead.org,
 kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, ryabinin.a.a@...il.com, vincenzo.frascino@....com
Subject: Re: [PATCH v2] mm: unexport globally copy_to_kernel_nofault

On 22.06.25 16:11, Sabyrzhan Tasbolatov wrote:
> `copy_to_kernel_nofault()` is an internal helper which should not be
> visible to loadable modules – exporting it would give exploit code a
> cheap oracle to probe kernel addresses.  Instead, keep the helper
> un-exported and compile the kunit case that exercises it only when
> `mm/kasan/kasan_test.o` is linked into vmlinux.
> 
> Fixes: ca79a00bb9a8 ("kasan: migrate copy_user_test to kunit")
> Suggested-by: Christoph Hellwig <hch@...radead.org>
> Suggested-by: Marco Elver <elver@...gle.com>
> Reviewed-by: Andrey Konovalov <andreyknvl@...il.com>
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@...il.com>
> ---

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb