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 A99A4C43334 for ; Tue, 7 Jun 2022 19:21:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355237AbiFGTT7 (ORCPT ); Tue, 7 Jun 2022 15:19:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35234 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352479AbiFGSbC (ORCPT ); Tue, 7 Jun 2022 14:31:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 023461451C3; Tue, 7 Jun 2022 10:56:14 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 957E3617B4; Tue, 7 Jun 2022 17:56:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1A433C341C8; Tue, 7 Jun 2022 17:56:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1654624573; bh=6nfGQcmOO+nzmnVXs7EuA6e3s87z59d7FQhJE3qTKds=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=U3dCBQhRy0QhANUmEic8904YlJw+FzkHYpzSjUF7NmAoAri6+rfG27E2ZIbS/HVLV 8Iv9eeHcOSXeug1vuX9oUGBPbGCjhVD6+7yMW+ZC0cC/JwpFIhSoWOpceulKBFeBHn z7g5fj/1eQNRESK4axpyEMJXt2ZQnaq1E7l6eCKvHdaMNyafk3PPZSIgKMk3XE99KC Gi6YWpnPiD8K7eudRXIgyjoSEqhTwAwxSqLgAlG1QL4Hh2K2rk8PTKxF+tDC4pEP2H 4wwuHVTPFpTPPymKcgzbIilAW0ACQVdWua+rJc87oOWddTzs8Q05RQYZrSgdF1a/Cs 7mePmWqnxOL7A== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kees Cook , Muhammad Usama Anjum , Arnd Bergmann , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 5.15 04/51] lkdtm/usercopy: Expand size of "out of frame" object Date: Tue, 7 Jun 2022 13:55:03 -0400 Message-Id: <20220607175552.479948-4-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220607175552.479948-1-sashal@kernel.org> References: <20220607175552.479948-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Kees Cook [ Upstream commit f387e86d3a74407bdd9c5815820ac9d060962840 ] To be sufficiently 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 Reviewed-by: Muhammad Usama Anjum Link: https://lore.kernel.org/lkml/762faf1b-0443-5ddf-4430-44a20cf2ec4d@collabora.com/ Signed-off-by: Kees Cook Signed-off-by: Sasha Levin --- drivers/misc/lkdtm/usercopy.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/drivers/misc/lkdtm/usercopy.c b/drivers/misc/lkdtm/usercopy.c index 9161ce7ed47a..3fead5efe523 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 +71,12 @@ static noinline void do_usercopy_stack(bool to_user, bool bad_frame) bad_stack -= sizeof(unsigned long); } +#ifdef ARCH_HAS_CURRENT_STACK_POINTER + pr_info("stack : %px\n", (void *)current_stack_pointer); +#endif + 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); -- 2.35.1