linux-kernel - Re: [PATCH 1/2] arm64/pageattr: Propagate return value from __change_memory

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Message-ID: <6bc0fac0-3c00-4ecf-948e-5648584ec939@arm.com>
Date: Thu, 13 Nov 2025 11:55:48 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Dev Jain <dev.jain@....com>, catalin.marinas@....com, will@...nel.org
Cc: rppt@...nel.org, shijie@...amperecomputing.com,
 yang@...amperecomputing.com, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] arm64/pageattr: Propagate return value from
 __change_memory_common

On 12/11/2025 06:27, Dev Jain wrote:
> The rodata=on security measure requires that any code path which does
> vmalloc -> set_memory_ro/set_memory_rox must protect the linear map alias
> too. Therefore, if such a call fails, we must abort set_memory_* and caller
> must take appropriate action; currently we are suppressing the error, and
> there is a real chance of such an error arising post commit a166563e7ec3
> ("arm64: mm: support large block mapping when rodata=full"). Therefore,
> propagate any error to the caller.
> 
> Fixes: a166563e7ec3 ("arm64: mm: support large block mapping when rodata=full")
> Signed-off-by: Dev Jain <dev.jain@....com>

Reviewed-by: Ryan Roberts <ryan.roberts@....com>

It would be good to get this into v6.18 I guess?

Although I think this will conflict with a patch from Yang that makes this work
with a partial vm area range - But I think that one will only go to v6.19.

Thanks,
Ryan

> ---
> v1 of this patch: https://lore.kernel.org/all/20251103061306.82034-1-dev.jain@arm.com/
> I have dropped stable since no real chance of failure was there.
> 
>  arch/arm64/mm/pageattr.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 5135f2d66958..b4ea86cd3a71 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -148,6 +148,7 @@ static int change_memory_common(unsigned long addr, int numpages,
>  	unsigned long size = PAGE_SIZE * numpages;
>  	unsigned long end = start + size;
>  	struct vm_struct *area;
> +	int ret;
>  	int i;
>  
>  	if (!PAGE_ALIGNED(addr)) {
> @@ -185,8 +186,10 @@ 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)) {
>  		for (i = 0; i < area->nr_pages; i++) {
> -			__change_memory_common((u64)page_address(area->pages[i]),
> +			ret = __change_memory_common((u64)page_address(area->pages[i]),
>  					       PAGE_SIZE, set_mask, clear_mask);
> +			if (ret)
> +				return ret;
>  		}
>  	}
>