linux-kernel - Re: [PATCH v1 1/5] mm: vmalloc must set pte via arch code

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Message-ID: <e414905a-8129-5c39-77cb-53fd75910440@arm.com>
Date:   Thu, 11 May 2023 14:14:11 +0100
From:   Ryan Roberts <ryan.roberts@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        SeongJae Park <sj@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        damon@...ts.linux.dev
Subject: Re: [PATCH v1 1/5] mm: vmalloc must set pte via arch code

My appologies for the noise: A blank line between Cc and Subject has broken the
subject and grouping in lore.

Please Ignore this, I will resend.


On 11/05/2023 13:58, Ryan Roberts wrote:
> It is bad practice to directly set pte entries within a pte table.
> Instead all modifications must go through arch-provided helpers such as
> set_pte_at() to give the arch code visibility and allow it to validate
> (and potentially modify) the operation.
> 
> Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function")
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  mm/vmalloc.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 9683573f1225..d8d2fe797c55 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2899,10 +2899,13 @@ struct vmap_pfn_data {
>  static int vmap_pfn_apply(pte_t *pte, unsigned long addr, void *private)
>  {
>  	struct vmap_pfn_data *data = private;
> +	pte_t ptent;
>  
>  	if (WARN_ON_ONCE(pfn_valid(data->pfns[data->idx])))
>  		return -EINVAL;
> -	*pte = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
> +
> +	ptent = pte_mkspecial(pfn_pte(data->pfns[data->idx++], data->prot));
> +	set_pte_at(&init_mm, addr, pte, ptent);
>  	return 0;
>  }
>