Subject: Re: [PATCH 1/9] mm: Hardened usercopy

From: Rik van Riel <[email-masked]>
Date: Thu, 07 Jul 2016 12:35:17 -0400

On Wed, 2016-07-06 at 15:25 -0700, Kees Cook wrote:
> 
> +	/* Allow kernel rodata region (if not marked as Reserved).
> */
> +	if (ptr >= (const void *)__start_rodata &&
> +	    end <= (const void *)__end_rodata)
> +		return NULL;
> 
One comment here.

__check_object_size gets "to_user" as an argument.

It may make sense to pass that to check_heap_object, and
only allow copy_to_user from rodata, never copy_from_user,
since that section should be read only.

> +void __check_object_size(const void *ptr, unsigned long n, bool
> to_user)
> +{
> 

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