linux-kernel - Re: [PATCH v7 6/7] mseal, system mappings: uprobe mapping

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Message-ID: <20250226163359.GB17833@redhat.com>
Date: Wed, 26 Feb 2025 17:33:59 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: jeffxu@...omium.org
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com,
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Subject: Re: [PATCH v7 6/7] mseal, system mappings: uprobe mapping

On 02/26, Oleg Nesterov wrote:
>
> On 02/24, jeffxu@...omium.org wrote:
> >
> > Unlike other system mappings, the uprobe mapping is not
> > established during program startup. However, its lifetime is the same
> > as the process's lifetime. It could be sealed from creation.
>
> Agreed, VM_SEALED should be always for the "[uprobes]" vma, regardless
> of config options.
>
> ACK,
>
> but can't we do
>
> 	#ifdef CONFIG_64BIT
> 	/* VM is sealed, in vm_flags */
> 	#define VM_SEALED	_BITUL(63)
> +	#else
> +	#define VM_SEALED	0
> 	#endif
>
> and then simply
>
> 	vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
> -				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
> +				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO|VM_SEALED,
>
> ?
>
> But I am fine either way, feel free to ignore.

Yes, but either way, why your patch adds "unsigned long vm_flags" ?
OK, perhaps it makes sense for readability, but

	vm_flags = VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO;
	vm_flags |= VM_SEALED_SYSMAP;

looks a bit strange, why not

	vm_flags = VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO|VM_SEALED_SYSMAP;

?

Oleg.