linux-kernel - Re: [PATCH v6 3/7] mseal, system mappings: enable x86-64

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Message-ID: <6kyr7f4huquncaofkwoyozpbj6svhpj5o2f375f6ohqlgyrq5n@urqssz5pca3r>
Date: Mon, 24 Feb 2025 16:06:40 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: jeffxu@...omium.org
Cc: akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com,
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Subject: Re: [PATCH v6 3/7] mseal, system mappings: enable x86-64

* jeffxu@...omium.org <jeffxu@...omium.org> [250224 12:45]:
> From: Jeff Xu <jeffxu@...omium.org>
> 
> Provide support for CONFIG_MSEAL_SYSTEM_MAPPINGS on x86-64,
> covering the vdso, vvar, vvar_vclock.
> 
> Production release testing passes on Android and Chrome OS.
> 
> Signed-off-by: Jeff Xu <jeffxu@...omium.org>
> ---
>  arch/x86/Kconfig          |  1 +
>  arch/x86/entry/vdso/vma.c | 16 ++++++++++------
>  2 files changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 87198d957e2f..8fa17032ca46 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -26,6 +26,7 @@ config X86_64
>  	depends on 64BIT
>  	# Options that are inherently 64-bit kernel only:
>  	select ARCH_HAS_GIGANTIC_PAGE
> +	select ARCH_HAS_MSEAL_SYSTEM_MAPPINGS
>  	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
>  	select ARCH_SUPPORTS_PER_VMA_LOCK
>  	select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> index 39e6efc1a9ca..54677964d0b5 100644
> --- a/arch/x86/entry/vdso/vma.c
> +++ b/arch/x86/entry/vdso/vma.c
> @@ -247,6 +247,7 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
>  	struct mm_struct *mm = current->mm;
>  	struct vm_area_struct *vma;
>  	unsigned long text_start;
> +	unsigned long vm_flags;
>  	int ret = 0;
>  
>  	if (mmap_write_lock_killable(mm))
> @@ -264,11 +265,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
>  	/*
>  	 * MAYWRITE to allow gdb to COW and set breakpoints
>  	 */
> +	vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC;
> +	vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG;
>  	vma = _install_special_mapping(mm,
>  				       text_start,
>  				       image->size,
> -				       VM_READ|VM_EXEC|
> -				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
> +				       vm_flags,

Why not just | VM_SEALED_SYSMAP here, and everywhere else?

>  				       &vdso_mapping);
>  
>  	if (IS_ERR(vma)) {
> @@ -276,11 +278,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
>  		goto up_fail;
>  	}
>  
> +	vm_flags = VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|VM_PFNMAP;
> +	vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG;
>  	vma = _install_special_mapping(mm,
>  				       addr,
>  				       (__VVAR_PAGES - VDSO_NR_VCLOCK_PAGES) * PAGE_SIZE,
> -				       VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
> -				       VM_PFNMAP,
> +				       vm_flags,
>  				       &vvar_mapping);
>  
>  	if (IS_ERR(vma)) {
> @@ -289,11 +292,12 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr)
>  		goto up_fail;
>  	}
>  
> +	vm_flags = VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|VM_PFNMAP;
> +	vm_flags |= MSEAL_SYSTEM_MAPPINGS_VM_FLAG;
>  	vma = _install_special_mapping(mm,
>  				       addr + (__VVAR_PAGES - VDSO_NR_VCLOCK_PAGES) * PAGE_SIZE,
>  				       VDSO_NR_VCLOCK_PAGES * PAGE_SIZE,
> -				       VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
> -				       VM_PFNMAP,
> +				       vm_flags,
>  				       &vvar_vclock_mapping);
>  
>  	if (IS_ERR(vma)) {
> -- 
> 2.48.1.601.g30ceb7b040-goog
>