linux-kernel - Re: [v2 PATCH] arm64: mm: make linear mapping permission update more robust for patial range

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Message-ID: <20251118230750.GA1451312@ax162>
Date: Tue, 18 Nov 2025 16:07:50 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Yang Shi <yang@...amperecomputing.com>
Cc: ryan.roberts@....com, dev.jain@....com, cl@...two.org,
	catalin.marinas@....com, will@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [v2 PATCH] arm64: mm: make linear mapping permission update more
 robust for patial range

On Tue, Nov 18, 2025 at 09:35:08AM -0800, Yang Shi wrote:
> Thanks for reporting this problem. It looks like I forgot to use untagged
> address when calculating idx.
> 
> Can you please try the below patch?
> 
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 08ac96b9f846..0f6417e3f9f1 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -183,7 +183,7 @@ static int change_memory_common(unsigned long addr, int
> numpages,
>          */
>         if (rodata_full && (pgprot_val(set_mask) == PTE_RDONLY ||
>                             pgprot_val(clear_mask) == PTE_RDONLY)) {
> -               unsigned long idx = (start - (unsigned long)area->addr) >>
> PAGE_SHIFT;
> +               unsigned long idx = (start - (unsigned
> long)kasan_reset_tag(area->addr)) >> PAGE_SHIFT;
>                 for (; numpages; idx++, numpages--) {
> __change_memory_common((u64)page_address(area->pages[idx]),
>                                                PAGE_SIZE, set_mask,
> clear_mask);

Yes, that appears to resolve the issue for me, thanks for the quick fix!

If a formal tag helps:

Tested-by: Nathan Chancellor <nathan@...nel.org>

Cheers,
Nathan