From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66104C433F5 for ; Wed, 16 Feb 2022 20:17:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229820AbiBPUSA (ORCPT ); Wed, 16 Feb 2022 15:18:00 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:52144 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230228AbiBPUR7 (ORCPT ); Wed, 16 Feb 2022 15:17:59 -0500 Received: from mail-pf1-x42f.google.com (mail-pf1-x42f.google.com [IPv6:2607:f8b0:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E1DD2569DA for ; Wed, 16 Feb 2022 12:17:46 -0800 (PST) Received: by mail-pf1-x42f.google.com with SMTP id l19so3084013pfu.2 for ; Wed, 16 Feb 2022 12:17:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1CQ3e4LmGdBNkn8J0Xh4T4TteU4rCgSYMdgdDt/RPvw=; b=lNyV9zSsZq+dmQhzA3T49jEEYBN5Jb7yWT/zVg9vqExqpGD7WQx1SOplo1xG4o73Nv gILh22iN3MXbvISnUP6DL+EmPnRXl8g8kC02mGS37echzeOABVHV3UdcHqyTFrkCLBCs do2CMs0rCFmfa8MswqyeaMg1mrvXei9x4Z1R0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1CQ3e4LmGdBNkn8J0Xh4T4TteU4rCgSYMdgdDt/RPvw=; b=lDBOzMrZ0auglhCLy7QFK5XqhBsc54hBW4Heo9UmTRSDNpa4+Sm6Tot89VES5rEKUW xoNJivdGCGtf8oMe5YsvLFAgJT3GnDtnaNXKScDxvwnJAjrBsKIwUwmRIuZoGr7yCwLB PHUEACz71JmluKyOHWp8av3UYMy4ZzV50doh7N8z76PGDfriC0LYbgiyKqfElp2YZiUU ZK1HOkFWE8IrZfLaLfqlnQ7GFcHPH3T6eXFmgSJ5Kkm09O0Qm3yvzmrEuM46yexj1/nx g1ai9JhyjCP7lZ5o05wbwt00wSnkPFSj80YGTmVu3tb/xkHxrZoYSOWBoQxy9iCbnwWH /j8A== X-Gm-Message-State: AOAM531gE93id20PUV8nYu2J/bDw3hIOtHc0n+jeilfR/R/ix38hQKl7 xZ/7AZ+/XdjkopMeud8kmD7r7w== X-Google-Smtp-Source: ABdhPJyC4Y5JXgGZidIXBFGAp800bP6PQMJWttROYEf/sXG4nwUaecw0o0cVJrygUfpVmp7a0Qfbhg== X-Received: by 2002:a63:6d0d:0:b0:370:14d8:5962 with SMTP id i13-20020a636d0d000000b0037014d85962mr3628788pgc.463.1645042665782; Wed, 16 Feb 2022 12:17:45 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id y20sm25544608pfi.87.2022.02.16.12.17.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Feb 2022 12:17:45 -0800 (PST) From: Kees Cook To: Muhammad Usama Anjum Cc: Kees Cook , Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] lkdtm/usercopy: Expand size of "out of frame" object Date: Wed, 16 Feb 2022 12:17:43 -0800 Message-Id: <20220216201743.2088344-1-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2224; h=from:subject; bh=8yZ/Tdt8BG4aUa0vMrljSrZbhWwVIs3OtFM0Be04X5o=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBiDVvmOtNUr/1pMc582pfphqTzlO2/tNfUWNp/07eP RxLKwmuJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYg1b5gAKCRCJcvTf3G3AJsz5EA CDVZlagFbsoFvCSozMc5toker3Thm4jAqHp65mLbE4x7bi/ruvQWqlKg0sf1p86bId0kASp8HY+0hX rDzz17rUWVoF8I4QlZuY5YdA5Nl6T+NSYlChzKn75aae0cHqgZ3K4gavZLlyck5/XMeJaJESPB1EKy EwmIgyTcqPSqke0ptePmqK3oUAf6yfyLYiHI6YSRF8/yzoZm/8YLFp7BCaUArhewrgwBqWEqwrdySE YfbwpwxscmC/18Da0I5FNwtcDNUXj0urKK7/uHS/it0bsseI+b6DopdetHp5m2HS3Xatie53pjzb+Z jWZVlZvE3Cx1uhyfkxJae80Sv559aJgeABOIRB1R5DnPwHTdemFFk/ze/hl0LnKma8mEZlDlWtrayH iPo8oPJb3zmXggO86vP/W7IXpsc3jbHRkViucszppZaThJ/Alu9BsmCIbHO9BWQbZ1JLvZpcCh4wRy ANeaYL5IYnfqw+us8gOmFFCX08MwVN5R9LboPt9RQ+LnxdAmVhs3xSj2i3T/qdkvX9rnVYdcz6FytU ouVc7RbAkj4TGwmJFbInCsDh0BbPKnZLBPXaYLQGZcrzPvHQF2Jhmc412cEwcKyo8nfQJiKLL82nYI jW6WV63iUqasstniiJN4Y8owHPJ3m2aENbfI4rixme3SuhhtMVm6hm3PRODQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org To be sufficient out of range for the usercopy test to see the lifetime mismatch, expand the size of the "bad" buffer, which will let it be beyond current_stack_pointer regardless of stack growth direction. Paired with the recent addition of stack depth checking under CONFIG_HARDENED_USERCOPY=y, this will correctly start tripping again. Reported-by: Muhammad Usama Anjum Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Signed-off-by: Kees Cook --- drivers/misc/lkdtm/usercopy.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c index 9161ce7ed47a..781345ea3b07 100644 --- a/drivers/misc/lkdtm/usercopy.c +++ b/drivers/misc/lkdtm/usercopy.c @@ -30,12 +30,12 @@ static const unsigned char test_text[] = "This is a test.\n"; */ static noinline unsigned char *trick_compiler(unsigned char *stack) { - return stack + 0; + return stack + unconst; } static noinline unsigned char *do_usercopy_stack_callee(int value) { - unsigned char buf[32]; + unsigned char buf[128]; int i; /* Exercise stack to avoid everything living in registers. */ @@ -43,7 +43,12 @@ static noinline unsigned char *do_usercopy_stack_callee(int value) buf[i] = value & 0xff; } - return trick_compiler(buf); + /* + * Put the target buffer in the middle of stack allocation + * so that we don't step on future stack users regardless + * of stack growth direction. + */ + return trick_compiler(&buf[(128/2)-32]); } static noinline void do_usercopy_stack(bool to_user, bool bad_frame) @@ -66,6 +71,10 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame) bad_stack -= sizeof(unsigned long); } + pr_info("stack : %px\n", (void *)current_stack_pointer); + pr_info("good_stack: %px-%px\n", good_stack, good_stack + sizeof(good_stack)); + pr_info("bad_stack : %px-%px\n", bad_stack, bad_stack + sizeof(good_stack)); + user_addr = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_ANONYMOUS | MAP_PRIVATE, 0); -- 2.30.2