linux-kernel - Re: [PATCH v2] powerpc/mm: Fix KUAP warning by providing copy_from_kernel_nofault

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Date:   Thu, 10 Dec 2020 11:23:57 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     akpm@...ux-foundation.org, hch@....de,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        viro@...iv.linux.org.uk,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2] powerpc/mm: Fix KUAP warning by providing copy_from_kernel_nofault_allowed()

On Mon, 7 Dec 2020 16:58:01 +0000 (UTC), Christophe Leroy wrote:
> Since commit c33165253492 ("powerpc: use non-set_fs based maccess
> routines"), userspace access is not granted anymore when using
> copy_from_kernel_nofault()
> 
> However, kthread_probe_data() uses copy_from_kernel_nofault()
> to check validity of pointers. When the pointer is NULL,
> it points to userspace, leading to a KUAP fault and triggering
> the following big hammer warning many times when you request
> a sysrq "show task":
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/mm: Fix KUAP warning by providing copy_from_kernel_nofault_allowed()
      https://git.kernel.org/powerpc/c/5eedf9fe8db23313df104576845cec5f481b9b60

cheers