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From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 17 Feb 2022 08:52:29 +0100
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Subject: Re: [PATCH v2 13/18] uaccess: generalize access_ok()
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On Wed, Feb 16, 2022 at 2:13 PM Arnd Bergmann <arnd@kernel.org> wrote:

> + * limit and catch all possible overflows.
> + * On architectures with separate user address space (m68k, s390, parisc,
> + * sparc64) or those without an MMU, this should always return true.
...
> +static inline int __access_ok(const void __user *ptr, unsigned long size)
> +{
> +       unsigned long limit = user_addr_max();
> +       unsigned long addr = (unsigned long)ptr;
> +
> +       if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE))
> +               return true;

I noticed that I'm missing the check for !CONFIG_MMU here, despite
mentioning that in the comment above it. I've added it now.

        Arnd