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

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Message-ID: <55a9ff15-c72e-45cb-ab38-ad814011e27e@lucifer.local>
Date: Tue, 25 Feb 2025 06:24:22 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.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 Mon, Feb 24, 2025 at 10:52:45PM +0000, jeffxu@...omium.org wrote:
> From: Jeff Xu <jeffxu@...omium.org>
>
> Provide support to mseal the uprobe mapping.
>
> 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.
>

I thought we agreed not to enable this for uprobes for now? What testing
have you done to ensure this is functional?

I mean is this literally _all_ uprobe mappings now being sealed?

I'd really like some more assurances on this one. And what are you
mitigating by sealing these? I get VDSO (kinda) but uprobes?

You really need to provide more justification here.

> Signed-off-by: Jeff Xu <jeffxu@...omium.org>
> ---
>  kernel/events/uprobes.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 2ca797cbe465..8dcdfa0d306b 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1662,6 +1662,7 @@ static const struct vm_special_mapping xol_mapping = {
>  static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
>  {
>  	struct vm_area_struct *vma;
> +	unsigned long vm_flags;
>  	int ret;
>
>  	if (mmap_write_lock_killable(mm))
> @@ -1682,8 +1683,10 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
>  		}
>  	}
>
> +	vm_flags = VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO;
> +	vm_flags |= VM_SEALED_SYSMAP;
>  	vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
> -				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
> +				vm_flags,
>  				&xol_mapping);
>  	if (IS_ERR(vma)) {
>  		ret = PTR_ERR(vma);
> --
> 2.48.1.658.g4767266eb4-goog
>