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

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Message-ID: <aSR1mn8jjzty5J9F@willie-the-truck>
Date: Mon, 24 Nov 2025 15:11:22 +0000
From: Will Deacon <will@...nel.org>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Dev Jain <dev.jain@....com>, catalin.marinas@....com, 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 Thu, Nov 13, 2025 at 11:55:48AM +0000, Ryan Roberts wrote:
> 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?

I'm not sure I see the urgency. When the commit message says:

  "there is a real chance of such an error arising post commit a166563e7ec3"

afaict that's either due to -ENOMEM or some hideous issue with the
page-tables (e.g. the -EINVALs in pageattr_pXd_entry() seem completely
unnecessary to me).

Do you think failure is actually likely and recoverable?

Will