linux-kernel - Re: [PATCH v23 18/28] mm/mmap: Add shadow stack pages to memory accounting

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Date:   Mon, 22 Mar 2021 13:57:29 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc:     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>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>
Subject: Re: [PATCH v23 18/28] mm/mmap: Add shadow stack pages to memory
 accounting

On Tue, Mar 16, 2021 at 08:10:44AM -0700, Yu-cheng Yu wrote:
> Account shadow stack pages to stack memory.
> 
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> ---
>  arch/x86/mm/pgtable.c   |  7 +++++++
>  include/linux/pgtable.h | 11 +++++++++++
>  mm/mmap.c               |  5 +++++
>  3 files changed, 23 insertions(+)
> 
> diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
> index 0f4fbf51a9fc..948d28c29964 100644
> --- a/arch/x86/mm/pgtable.c
> +++ b/arch/x86/mm/pgtable.c
> @@ -895,3 +895,10 @@ int pmd_free_pte_page(pmd_t *pmd, unsigned long addr)
>  
>  #endif /* CONFIG_X86_64 */
>  #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
> +
> +#ifdef CONFIG_ARCH_HAS_SHADOW_STACK
> +bool arch_shadow_stack_mapping(vm_flags_t vm_flags)
> +{
> +	return (vm_flags & VM_SHSTK);
> +}
> +#endif
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index cbd98484c4f1..487c08df4365 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -1470,6 +1470,17 @@ static inline pmd_t arch_maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma
>  #endif /* CONFIG_ARCH_MAYBE_MKWRITE */
>  #endif /* CONFIG_MMU */
>  
> +#ifdef CONFIG_MMU
> +#ifdef CONFIG_ARCH_HAS_SHADOW_STACK
> +bool arch_shadow_stack_mapping(vm_flags_t vm_flags);
> +#else
> +static inline bool arch_shadow_stack_mapping(vm_flags_t vm_flags)
> +{
> +	return false;
> +}
> +#endif /* CONFIG_ARCH_HAS_SHADOW_STACK */
> +#endif /* CONFIG_MMU */
> +
>  /*
>   * Architecture PAGE_KERNEL_* fallbacks
>   *
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 3f287599a7a3..2ac67882ace2 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1718,6 +1718,9 @@ static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
>  	if (file && is_file_hugepages(file))
>  		return 0;
>  
> +	if (arch_shadow_stack_mapping(vm_flags))
> +		return 1;
> +

What's wrong with testing (vm_flags & VM_SHSTK) here? VM_SHSTK is 0 on
non-x86.

>  	return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
>  }
>  
> @@ -3387,6 +3390,8 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
>  		mm->stack_vm += npages;
>  	else if (is_data_mapping(flags))
>  		mm->data_vm += npages;
> +	else if (arch_shadow_stack_mapping(flags))
> +		mm->stack_vm += npages;

Ditto.

>  }
>  
>  static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
> -- 
> 2.21.0
> 

-- 
 Kirill A. Shutemov