Re: [PATCH v2] mm: do not export ioremap_page_range symbol for external module

[Michal Hocko <mhocko@kernel.org>]

On Mon 23-01-17 20:07:00, zhongjiang wrote:
> From: zhong jiang <zhongjiang@huawei.com>
> 
> Recently, I've found cases in which ioremap_page_range was used
> incorrectly, in external modules, leading to crashes. This can be
> partly attributed to the fact that ioremap_page_range is lower-level,
> with fewer protections, as compared to the other functions that an
> external module would typically call. Those include:
> 
>      ioremap_cache
>      ioremap_nocache
>      ioremap_prot
>      ioremap_uc
>      ioremap_wc
>      ioremap_wt
> 
> ...each of which wraps __ioremap_caller, which in turn provides a
> safer way to achieve the mapping.
> 
> Therefore, stop EXPORT-ing ioremap_page_range.
> 
> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com> 
> Suggested-by: John Hubbard <jhubbard@nvidia.com>

git grep says that there are few direct users of this API in the tree.
Have you checked all of them? The export has been added by 81e88fdc432a
("ACPI, APEI, Generic Hardware Error Source POLL/IRQ/NMI notification
type support").

Other than that this looks reasonably to me.

> ---
>  lib/ioremap.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/lib/ioremap.c b/lib/ioremap.c
> index 86c8911..a3e14ce 100644
> --- a/lib/ioremap.c
> +++ b/lib/ioremap.c
> @@ -144,4 +144,3 @@ int ioremap_page_range(unsigned long addr,
>  
>  	return err;
>  }
> -EXPORT_SYMBOL_GPL(ioremap_page_range);
> -- 
> 1.8.3.1

-- 
Michal Hocko
SUSE Labs

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