From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) by kanga.kvack.org (Postfix) with ESMTP id B45416B0007 for ; Tue, 14 Aug 2018 08:30:18 -0400 (EDT) Received: by mail-pf1-f199.google.com with SMTP id s1-v6so11240149pfm.22 for ; Tue, 14 Aug 2018 05:30:18 -0700 (PDT) Received: from huawei.com (szxga04-in.huawei.com. [45.249.212.190]) by mx.google.com with ESMTPS id p24-v6si16336360plo.52.2018.08.14.05.30.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 14 Aug 2018 05:30:17 -0700 (PDT) From: Xiaofeng Yuan Subject: [PATCH RFC] usercopy: optimize stack check flow when the page-spanning test is disabled Date: Tue, 14 Aug 2018 20:20:28 +0800 Message-ID: <1534249228-57122-1-git-send-email-yuanxiaofeng1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: keescook@chromium.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaofeng Yuan The check_heap_object() checks the spanning multiple pages and slab. When the page-spanning test is disabled, the check_heap_object() is redundant for spanning multiple pages. However, the kernel stacks are multiple pages under certain conditions: CONFIG_ARCH_THREAD_STACK_ALLOCATOR is not defined and (THREAD_SIZE >= PAGE_SIZE). At this point, We can skip the check_heap_object() for kernel stacks to improve performance. Similarly, the virtually-mapped stack can skip check_heap_object() also, beacause virt_addr_valid() will return. I launched more than 100 apps on smartphone, and recorded total check time and numbers of kernel stacks. The average time of checking kernel stacks reduced by 48%. Signed-off-by: Xiaofeng Yuan --- mm/usercopy.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/mm/usercopy.c b/mm/usercopy.c index e9e9325..af350f6 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -255,6 +255,29 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) /* Check for invalid addresses. */ check_bogus_address((const unsigned long)ptr, n, to_user); +#if !defined(CONFIG_HARDENED_USERCOPY_PAGESPAN) && \ + !defined(CONFIG_ARCH_THREAD_STACK_ALLOCATOR) && \ + (THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)) + /* Check for bad stack object. */ + switch (check_stack_object(ptr, n)) { + case NOT_STACK: + /* Object is not touching the current process stack. */ + break; + case GOOD_FRAME: + case GOOD_STACK: + /* + * Object is either in the correct frame (when it + * is possible to check) or just generally on the + * process stack (when frame checking not available). + */ + return; + default: + usercopy_abort("process stack", NULL, to_user, 0, n); + } + + /* Check for bad heap object. */ + check_heap_object(ptr, n, to_user); +#else /* Check for bad heap object. */ check_heap_object(ptr, n, to_user); @@ -274,6 +297,7 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) default: usercopy_abort("process stack", NULL, to_user, 0, n); } +#endif /* Check for object in kernel to avoid text exposure. */ check_kernel_text_object((const unsigned long)ptr, n, to_user); -- 1.9.1