linux-kernel - Re: [PATCH v3 6/9] module: switch to execmem API for remapping as RW and restoring ROX

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Message-ID: <021665c5-b017-415f-ad2b-0131dcc81068@suse.com>
Date: Mon, 27 Jan 2025 13:50:31 +0100
From: Petr Pavlu <petr.pavlu@...e.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: x86@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
 Andy Lutomirski <luto@...nel.org>,
 Anton Ivanov <anton.ivanov@...bridgegreys.com>,
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Subject: Re: [PATCH v3 6/9] module: switch to execmem API for remapping as RW
 and restoring ROX

On 1/26/25 08:47, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
> 
> Instead of using writable copy for module text sections, temporarily remap
> the memory allocated from execmem's ROX cache as writable and restore its
> ROX permissions after the module is formed.
> 
> This will allow removing nasty games with writable copy in alternatives
> patching on x86.
> 
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

[...]

> +static void module_memory_restore_rox(struct module *mod)
> +{
> +	for_class_mod_mem_type(type, text) {
> +		struct module_memory *mem = &mod->mem[type];
> +
> +		if (mem->is_rox)
> +			execmem_restore_rox(mem->base, mem->size);
> +	}
> +}
> +

Can the execmem_restore_rox() call here fail? I realize that there isn't
much that the module loader can do if that happens, but should it be
perhaps logged as a warning?

-- 
Thanks,
Petr