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 X-Spam-Level: X-Spam-Status: No, score=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42CFAC433E6 for ; Wed, 3 Feb 2021 00:32:09 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DF87D64F6A for ; Wed, 3 Feb 2021 00:32:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DF87D64F6A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ozlabs.ru Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4DVjLF5sg2zDqL5 for ; Wed, 3 Feb 2021 11:32:05 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.ru (client-ip=107.174.27.60; helo=ozlabs.ru; envelope-from=aik@ozlabs.ru; receiver=) Received: from ozlabs.ru (ozlabs.ru [107.174.27.60]) by lists.ozlabs.org (Postfix) with ESMTP id 4DVK0d60vszDrcG for ; Tue, 2 Feb 2021 20:15:25 +1100 (AEDT) Received: from fstn1-p1.ozlabs.ibm.com (localhost [IPv6:::1]) by ozlabs.ru (Postfix) with ESMTP id 3E61DAE80014; Tue, 2 Feb 2021 04:14:49 -0500 (EST) From: Alexey Kardashevskiy To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH kernel] powerpc/uaccess: Skip might_fault() when user access is enabled Date: Tue, 2 Feb 2021 20:14:47 +1100 Message-Id: <20210202091447.36234-1-aik@ozlabs.ru> X-Mailer: git-send-email 2.17.1 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" The amount of code executed with enabled user space access (unlocked KUAP) should be minimal. However with CONFIG_PROVE_LOCKING or CONFIG_DEBUG_ATOMIC_SLEEP enabled, might_fault() may end up replaying interrupts which in turn may access the user space and forget to restore the KUAP state. The problem places are strncpy_from_user (and similar) which unlock KUAP and call unsafe_get_user -> __get_user_allowed -> __get_user_nocheck() with do_allow=false to skip KUAP as the caller took care of it. This changes __get_user_nocheck() to look at @do_allow to decide whether to skip might_fault(). Since strncpy_from_user/etc call might_fault() anyway before unlocking KUAP, there should be no visible change. Signed-off-by: Alexey Kardashevskiy --- This an attempt to fix that KUAP restore problem from "powerpc/kuap: Restore AMR after replaying soft interrupts". --- arch/powerpc/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 501c9a79038c..cd6c0427a9e2 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -313,7 +313,7 @@ do { \ __typeof__(size) __gu_size = (size); \ \ __chk_user_ptr(__gu_addr); \ - if (!is_kernel_addr((unsigned long)__gu_addr)) \ + if (!do_allow && !is_kernel_addr((unsigned long)__gu_addr)) \ might_fault(); \ barrier_nospec(); \ if (do_allow) \ -- 2.17.1