Re: [PATCH] x86/sgx: Fix free_cnt counting logic in epc section

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