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 AD8D2C433F5 for ; Wed, 16 Feb 2022 20:14:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230141AbiBPUPH (ORCPT ); Wed, 16 Feb 2022 15:15:07 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:46140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230083AbiBPUPF (ORCPT ); Wed, 16 Feb 2022 15:15:05 -0500 Received: from mail-pl1-x62a.google.com (mail-pl1-x62a.google.com [IPv6:2607:f8b0:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3966D235865 for ; Wed, 16 Feb 2022 12:14:52 -0800 (PST) Received: by mail-pl1-x62a.google.com with SMTP id x11so2831762pll.10 for ; Wed, 16 Feb 2022 12:14:52 -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=xqE2BW0tKVRqM9ZhCDPXCovwSbjof6cI+9q/oGqooSk=; b=NR7TiaIkVeb6mYv4qWdPa8tE15JoCJw13yejHxDLUfmlF0RP3HlJZPJp7inuchCg3k bLOz3ieHHziV0osXGKcv6SubQC2ZeptScXKgpr+t4GS9WZQjM/OHtElPdNEb4YVPKp3C BgrrSZdkcsm8IgTQG6Cl2WHciGSaYcw2pV+NY= 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=xqE2BW0tKVRqM9ZhCDPXCovwSbjof6cI+9q/oGqooSk=; b=ssX9heMZwi5r9j3pwWnuOVIyHYdyHXruTHeL10mCu7QwffcGuRJMMfXglHA2PrYe0j 4uLfbGNep9189iZ83hrFLLaToJ1+/5scC670mW6X4SuW4oRGE4j8z5MDFDuumSVVrocY 8rerUMYykqFrLKsnXw1/3v0DEV15qCkG2tYe5C+0mD/GmK5FQGGtmFoes1YZ2ng15seq U/4JIokIXxbLtHJMshuWMqPZP3C2hhMSMKZ+3+JO1LcfT6SpID83clFBq/Nh5A3yxKtN +9X4B4oElIURA5MzP2NQh1hLTUH/d+tmIj5so+UGJ+Shue4GiCpBkesJPcvskKvk5whp j3gg== X-Gm-Message-State: AOAM530eUtg5wGqJFtgR9YavONKLXKNzZIMLqfO8+4SKvgIg2M37Uj7H IwgcrD+x7QrKppuREEhO20xnxg== X-Google-Smtp-Source: ABdhPJwIU2Fu/iRv2C0QJmBs5y1p/RE21NXtauVHjHeLf70sjR3+jCzd9e3ecNuE5/iHmiiSBEDwiQ== X-Received: by 2002:a17:90b:4004:b0:1b8:b2eb:4b83 with SMTP id ie4-20020a17090b400400b001b8b2eb4b83mr3691254pjb.149.1645042491710; Wed, 16 Feb 2022 12:14:51 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id t1sm5964516pgj.43.2022.02.16.12.14.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Feb 2022 12:14:51 -0800 (PST) From: Kees Cook To: Muhammad Usama Anjum Cc: Kees Cook , Matthew Wilcox , Josh Poimboeuf , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] usercopy: Check valid lifetime via stack depth Date: Wed, 16 Feb 2022 12:14:49 -0800 Message-Id: <20220216201449.2087956-1-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2777; h=from:subject; bh=jr1yKp0UMwd5gvvB/ePD/2FkWdtbd+ZCUu7BnVQyulA=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBiDVs4Hh87CYY9W3rMbKqyfd7+UszuGa3FFWxH8s9m q2FNCVaJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYg1bOAAKCRCJcvTf3G3AJttLD/ wNKTVOmCoYdtqtUSIlcd62hL/1Pq8cEu2EynIeBUQSn25cWzaTcMQu47PDzckY8hcz2F6ZCQSrlf2s EGpOHPUFK6E+Yk7LHpnLGg7P/NS3DzdGE7uixLZmooHCROncIbDIsvWDDpX5rKKNACSRKVf9Rx/1PI pnLyZUzDNVtwQK9XDphmrat0BKjWb3OTB7vbbtDz8bkVZnN1IS+eMSbEraPpeRY6Vl0jwktEK5jTRm q29MZlM2AB9X/EuFrzaoR6jXQ7CDtPg7klR/gSM/eQht6pH7UY6HsUqofFfbYziHjFCMzYnxMRZHf6 Cx0cXvZbjrOnzsyoVBdhM1003MSKtlEuUVT8p31J88qXf5d9uvRK/Sj9gFvBWiyxtcpV8Lwf4pOsb1 sBFN0hJ6kaIZoYi+LNf3K2QLBfXymjowRa5WKzhKzzQQxlBdTr5Gt+0UWcyyvjAK4J9IB3BEuo8sbT RAzGeMq122044mgIkhYN7M7rvd5stZnzgA0BOMpFQjvJsdSso5ovUlW46vqQYpWAxEEPhsFNKaICo8 hRnGOa70iGY7KvgyEt/0ePSl2MlN8s2gfyv5dDPGwbjmN/05WKk3zYB2hFPEjZ0uVY19Rv8G13AaMs xHMo/2VEcpc4rQd9KR0qW3usVDOF84bmQwX5tD/twu+aFsKbBov8rVBuORNg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Under CONFIG_HARDENED_USERCOPY=y, when exact stack frame boundary checking is not available (i.e. everything except x86 with FRAME_POINTER), check a stack object as being at least "current depth valid", in the sense that any object within the stack region but not between start-of-stack and current_stack_pointer should be considered unavailable (i.e. its lifetime is from a call no longer present on the stack). Additionally report usercopy bounds checking failures with an offset from current_stack_pointer, which may assist with diagnosing failures. The LKDTM USERCOPY_STACK_FRAME_TO and USERCOPY_STACK_FRAME_FROM tests (once slightly adjusted in a separate patch) will pass again with this fixed. Cc: Muhammad Usama Anjum Cc: Matthew Wilcox (Oracle) Cc: Josh Poimboeuf Cc: Andrew Morton Cc: linux-mm@kvack.org Signed-off-by: Kees Cook --- mm/usercopy.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/mm/usercopy.c b/mm/usercopy.c index d0d268135d96..3846c1634dca 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -29,13 +29,20 @@ * Returns: * NOT_STACK: not at all on the stack * GOOD_FRAME: fully within a valid stack frame - * GOOD_STACK: fully on the stack (when can't do frame-checking) + * GOOD_STACK: within the current stack (when can't frame-check exactly) * BAD_STACK: error condition (invalid stack position or bad stack frame) */ static noinline int check_stack_object(const void *obj, unsigned long len) { const void * const stack = task_stack_page(current); const void * const stackend = stack + THREAD_SIZE; +#ifndef CONFIG_STACK_GROWSUP + const void * const high = stackend; + const void * const low = (void *)current_stack_pointer; +#else + const void * const high = (void *)current_stack_pointer; + const void * const low = stack; +#endif int ret; /* Object is not on the stack at all. */ @@ -55,6 +62,12 @@ static noinline int check_stack_object(const void *obj, unsigned long len) if (ret) return ret; + /* + * Reject: object not within current stack depth. + */ + if (obj < low || high < obj + len) + return BAD_STACK; + return GOOD_STACK; } @@ -280,7 +293,13 @@ void __check_object_size(const void *ptr, unsigned long n, bool to_user) */ return; default: - usercopy_abort("process stack", NULL, to_user, 0, n); + usercopy_abort("process stack", NULL, to_user, +#ifndef CONFIG_STACK_GROWSUP + (void *)current_stack_pointer - ptr, +#else + ptr - (void *)current_stack_pointer, +#endif + n); } /* Check for bad heap object. */ -- 2.30.2