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* [PATCH] x86/sgx: Fix free_cnt counting logic in epc section
@ 2021-01-18 13:33 Tianjia Zhang
  2021-01-19 20:24 ` Sean Christopherson
  2021-01-20 14:36 ` Jarkko Sakkinen
  0 siblings, 2 replies; 3+ messages in thread
From: Tianjia Zhang @ 2021-01-18 13:33 UTC (permalink / raw)
  To: Jarkko Sakkinen, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
	H. Peter Anvin, Andrew Morton, Shuah Khan, haitao.huang,
	Kai Huang, x86, linux-sgx, linux-kernel, linux-mm,
	linux-kselftest, Jia Zhang
  Cc: Tianjia Zhang

Increase `section->free_cnt` in sgx_sanitize_section() is
more reasonable, which is called in ksgxd kernel thread,
instead of assigning it to epc section pages number at
initialization. Although this is unlikely to fail, these
pages cannot be allocated after initialization, and which
need to be reset by ksgxd.

Reported-by: Jia Zhang <zhang.jia@linux.alibaba.com>
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
---
 arch/x86/kernel/cpu/sgx/main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index c519fc5f6948..9e9a3cf7c00b 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -48,9 +48,10 @@ static void sgx_sanitize_section(struct sgx_epc_section *section)
 					struct sgx_epc_page, list);
 
 		ret = __eremove(sgx_get_epc_virt_addr(page));
-		if (!ret)
+		if (!ret) {
 			list_move(&page->list, &section->page_list);
-		else
+			section->free_cnt += 1;
+		} else
 			list_move_tail(&page->list, &dirty);
 
 		spin_unlock(&section->lock);
@@ -646,7 +647,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
 		list_add_tail(&section->pages[i].list, &section->init_laundry_list);
 	}
 
-	section->free_cnt = nr_pages;
 	return true;
 }
 
-- 
2.19.1.3.ge56e4f7


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [PATCH] x86/sgx: Fix free_cnt counting logic in epc section
  2021-01-18 13:33 [PATCH] x86/sgx: Fix free_cnt counting logic in epc section Tianjia Zhang
@ 2021-01-19 20:24 ` Sean Christopherson
  2021-01-20 14:36 ` Jarkko Sakkinen
  1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2021-01-19 20:24 UTC (permalink / raw)
  To: Tianjia Zhang
  Cc: Jarkko Sakkinen, Thomas Gleixner, Ingo Molnar, Borislav Petkov,
	H. Peter Anvin, Andrew Morton, Shuah Khan, haitao.huang,
	Kai Huang, x86, linux-sgx, linux-kernel, linux-mm,
	linux-kselftest, Jia Zhang

On Mon, Jan 18, 2021, Tianjia Zhang wrote:
> Increase `section->free_cnt` in sgx_sanitize_section() is
> more reasonable, which is called in ksgxd kernel thread,
> instead of assigning it to epc section pages number at
> initialization. Although this is unlikely to fail, these
> pages cannot be allocated after initialization, and which
> need to be reset by ksgxd.
> 
> Reported-by: Jia Zhang <zhang.jia@linux.alibaba.com>
> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>

Reviewed-by: Sean Christopherson <seanjc@google.com> 

> ---
>  arch/x86/kernel/cpu/sgx/main.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index c519fc5f6948..9e9a3cf7c00b 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -48,9 +48,10 @@ static void sgx_sanitize_section(struct sgx_epc_section *section)
>  					struct sgx_epc_page, list);
>  
>  		ret = __eremove(sgx_get_epc_virt_addr(page));
> -		if (!ret)
> +		if (!ret) {
>  			list_move(&page->list, &section->page_list);
> -		else
> +			section->free_cnt += 1;
> +		} else

Nit: the the "else" should also have curly braces.

>  			list_move_tail(&page->list, &dirty);
>  
>  		spin_unlock(&section->lock);

FWIW, taking section->lock could be moved inside the !ret flow so that EREMOVE
is done without holding the lock.  I've no idea if that'd actually change
anything in practice, but it's theoretically possible that ksgxd hasn't finished
sanitizing the EPC when userspace starts creating enclaves.

> @@ -646,7 +647,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
>  		list_add_tail(&section->pages[i].list, &section->init_laundry_list);
>  	}
>  
> -	section->free_cnt = nr_pages;
>  	return true;
>  }
>  
> -- 
> 2.19.1.3.ge56e4f7
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] x86/sgx: Fix free_cnt counting logic in epc section
  2021-01-18 13:33 [PATCH] x86/sgx: Fix free_cnt counting logic in epc section Tianjia Zhang
  2021-01-19 20:24 ` Sean Christopherson
@ 2021-01-20 14:36 ` Jarkko Sakkinen
  1 sibling, 0 replies; 3+ messages in thread
From: Jarkko Sakkinen @ 2021-01-20 14:36 UTC (permalink / raw)
  To: Tianjia Zhang
  Cc: Thomas Gleixner, Ingo Molnar, Borislav Petkov, H. Peter Anvin,
	Andrew Morton, Shuah Khan, haitao.huang, Kai Huang, x86,
	linux-sgx, linux-kernel, linux-mm, linux-kselftest, Jia Zhang

On Mon, Jan 18, 2021 at 09:33:47PM +0800, Tianjia Zhang wrote:
> Increase `section->free_cnt` in sgx_sanitize_section() is
> more reasonable, which is called in ksgxd kernel thread,
> instead of assigning it to epc section pages number at
> initialization. Although this is unlikely to fail, these
> pages cannot be allocated after initialization, and which
> need to be reset by ksgxd.
> 
> Reported-by: Jia Zhang <zhang.jia@linux.alibaba.com>
> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>

There is nothing broken in the logic. Convince me otherwise.

I.e. what is exactly broken, and how?

/Jarkko

> ---
>  arch/x86/kernel/cpu/sgx/main.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index c519fc5f6948..9e9a3cf7c00b 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -48,9 +48,10 @@ static void sgx_sanitize_section(struct sgx_epc_section *section)
>  					struct sgx_epc_page, list);
>  
>  		ret = __eremove(sgx_get_epc_virt_addr(page));
> -		if (!ret)
> +		if (!ret) {
>  			list_move(&page->list, &section->page_list);
> -		else
> +			section->free_cnt += 1;
> +		} else
>  			list_move_tail(&page->list, &dirty);
>  
>  		spin_unlock(&section->lock);
> @@ -646,7 +647,6 @@ static bool __init sgx_setup_epc_section(u64 phys_addr, u64 size,
>  		list_add_tail(&section->pages[i].list, &section->init_laundry_list);
>  	}
>  
> -	section->free_cnt = nr_pages;
>  	return true;
>  }
>  
> -- 
> 2.19.1.3.ge56e4f7
> 
> 

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-01-20 14:38 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-01-18 13:33 [PATCH] x86/sgx: Fix free_cnt counting logic in epc section Tianjia Zhang
2021-01-19 20:24 ` Sean Christopherson
2021-01-20 14:36 ` Jarkko Sakkinen

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