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 DB2C8C433EF for ; Mon, 13 Jun 2022 10:32:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344824AbiFMKb5 (ORCPT ); Mon, 13 Jun 2022 06:31:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34152 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244699AbiFMK07 (ORCPT ); Mon, 13 Jun 2022 06:26:59 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9AA8E248CA; Mon, 13 Jun 2022 03:19:49 -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 33E926066C; Mon, 13 Jun 2022 10:19:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 41275C34114; Mon, 13 Jun 2022 10:19:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655115588; bh=lQx9gW3Yr7Nl5zsN5pDITSvemx1zVOWZTy2c3CMR3ts=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Azb3X6LM7zuOlSeCHDmrAdQwaXUgpe52RqMsYewzoEbuIbQXrbAlbQ88eTv8XpEDy 3owlHCOPCnhS8prNrNM901JDA8dRzV0zacaCfkDkOB4vSgupQuyVEf6W6TahdmGX4z jCPw2dIX6NnLSmq+db3vzaWIoXcUEoxw6hP+OuXk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Muhammad Usama Anjum , Arnd Bergmann , Kees Cook , Sasha Levin Subject: [PATCH 4.9 139/167] lkdtm/usercopy: Expand size of "out of frame" object Date: Mon, 13 Jun 2022 12:10:13 +0200 Message-Id: <20220613094913.433606444@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094840.720778945@linuxfoundation.org> References: <20220613094840.720778945@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 1dd611423d8b..36438947244d 100644 --- a/drivers/misc/lkdtm_usercopy.c +++ b/drivers/misc/lkdtm_usercopy.c @@ -28,12 +28,12 @@ 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. */ @@ -41,7 +41,12 @@ 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) @@ -64,6 +69,12 @@ 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