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Date: Wed, 14 Jun 2023 10:50:34 +0200
From: David Hildenbrand <david@...hat.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>, x86@...nel.org,
"H . Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-mm@...ck.org,
linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>,
Andy Lutomirski <luto@...nel.org>,
Balbir Singh <bsingharora@...il.com>,
Borislav Petkov <bp@...en8.de>,
Cyrill Gorcunov <gorcunov@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Eugene Syromiatnikov <esyr@...hat.com>,
Florian Weimer <fweimer@...hat.com>,
"H . J . Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Nadav Amit <nadav.amit@...il.com>,
Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
Peter Zijlstra <peterz@...radead.org>,
Randy Dunlap <rdunlap@...radead.org>,
Weijiang Yang <weijiang.yang@...el.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
John Allen <john.allen@....com>, kcc@...gle.com,
eranian@...gle.com, rppt@...nel.org, jamorris@...ux.microsoft.com,
dethoma@...rosoft.com, akpm@...ux-foundation.org,
Andrew.Cooper3@...rix.com, christina.schimpe@...el.com,
debug@...osinc.com, szabolcs.nagy@....com,
torvalds@...ux-foundation.org, broonie@...nel.org
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>,
Pengfei Xu <pengfei.xu@...el.com>
Subject: Re: [PATCH v9 14/42] mm: Introduce VM_SHADOW_STACK for shadow stack
memory
On 13.06.23 02:10, Rick Edgecombe wrote:
> From: Yu-cheng Yu <yu-cheng.yu@...el.com>
>
> New hardware extensions implement support for shadow stack memory, such
> as x86 Control-flow Enforcement Technology (CET). Add a new VM flag to
> identify these areas, for example, to be used to properly indicate shadow
> stack PTEs to the hardware.
>
> Shadow stack VMA creation will be tightly controlled and limited to
> anonymous memory to make the implementation simpler and since that is all
> that is required. The solution will rely on pte_mkwrite() to create the
> shadow stack PTEs, so it will not be required for vm_get_page_prot() to
> learn how to create shadow stack memory. For this reason document that
> VM_SHADOW_STACK should not be mixed with VM_SHARED.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> Co-developed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
> Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Acked-by: Mike Rapoport (IBM) <rppt@...nel.org>
> Tested-by: Pengfei Xu <pengfei.xu@...el.com>
> Tested-by: John Allen <john.allen@....com>
> Tested-by: Kees Cook <keescook@...omium.org>
> ---
> Documentation/filesystems/proc.rst | 1 +
> fs/proc/task_mmu.c | 3 +++
> include/linux/mm.h | 8 ++++++++
> 3 files changed, 12 insertions(+)
>
> diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> index 7897a7dafcbc..6ccb57089a06 100644
> --- a/Documentation/filesystems/proc.rst
> +++ b/Documentation/filesystems/proc.rst
> @@ -566,6 +566,7 @@ encoded manner. The codes are the following:
> mt arm64 MTE allocation tags are enabled
> um userfaultfd missing tracking
> uw userfaultfd wr-protect tracking
> + ss shadow stack page
> == =======================================
>
> Note that there is no guarantee that every flag and associated mnemonic will
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 420510f6a545..38b19a757281 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -711,6 +711,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
> #ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
> [ilog2(VM_UFFD_MINOR)] = "ui",
> #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_MINOR */
> +#ifdef CONFIG_X86_USER_SHADOW_STACK
> + [ilog2(VM_SHADOW_STACK)] = "ss",
> +#endif
> };
> size_t i;
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 6f52c1e7c640..fb17cbd531ac 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -319,11 +319,13 @@ extern unsigned int kobjsize(const void *objp);
> #define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures */
> #define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */
> #define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectures */
> +#define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectures */
> #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0)
> #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1)
> #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2)
> #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3)
> #define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
> +#define VM_HIGH_ARCH_5 BIT(VM_HIGH_ARCH_BIT_5)
> #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
>
> #ifdef CONFIG_ARCH_HAS_PKEYS
> @@ -339,6 +341,12 @@ extern unsigned int kobjsize(const void *objp);
> #endif
> #endif /* CONFIG_ARCH_HAS_PKEYS */
>
> +#ifdef CONFIG_X86_USER_SHADOW_STACK
> +# define VM_SHADOW_STACK VM_HIGH_ARCH_5 /* Should not be set with VM_SHARED */
> +#else
> +# define VM_SHADOW_STACK VM_NONE
> +#endif
> +
> #if defined(CONFIG_X86)
> # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */
> #elif defined(CONFIG_PPC)
Acked-by: David Hildenbrand <david@...hat.com>
--
Cheers,
David / dhildenb
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