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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 B088CC28CC0 for ; Wed, 29 May 2019 12:34:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 930FA217D9 for ; Wed, 29 May 2019 12:34:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727056AbfE2Meq (ORCPT ); Wed, 29 May 2019 08:34:46 -0400 Received: from foss.arm.com ([217.140.101.70]:45032 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725914AbfE2Mep (ORCPT ); Wed, 29 May 2019 08:34:45 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6B81BA78; Wed, 29 May 2019 05:34:45 -0700 (PDT) Received: from p8cg001049571a15.blr.arm.com (p8cg001049571a15.blr.arm.com [10.162.41.181]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 6A3943F59C; Wed, 29 May 2019 05:34:42 -0700 (PDT) From: Anshuman Khandual To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Anshuman Khandual , Catalin Marinas , Will Deacon , Mark Rutland , James Morse , Andrey Konovalov Subject: [PATCH 1/4] arm64/mm: Drop mmap_sem before calling __do_kernel_fault() Date: Wed, 29 May 2019 18:04:42 +0530 Message-Id: <1559133285-27986-2-git-send-email-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> References: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is an inconsistency between down_read_trylock() success and failure paths while dealing with kernel access for non exception table areas where it calls __do_kernel_fault(). In case of failure it just bails out without holding mmap_sem but when it succeeds it does so while holding mmap_sem. Fix this inconsistency by just dropping mmap_sem in success path as well. __do_kernel_fault() calls die_kernel_fault() which then calls show_pte(). show_pte() in this path might become bit more unreliable without holding mmap_sem. But there are already instances [1] in do_page_fault() where die_kernel_fault() gets called without holding mmap_sem. show_pte() can be made more robust independently but in a later patch. [1] Conditional block for (is_ttbr0_addr && is_el1_permission_fault) Signed-off-by: Anshuman Khandual Cc: Catalin Marinas Cc: Will Deacon Cc: Mark Rutland Cc: James Morse Cc: Andrey Konovalov --- arch/arm64/mm/fault.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index a30818e..dc1cf32 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -503,8 +503,10 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, */ might_sleep(); #ifdef CONFIG_DEBUG_VM - if (!user_mode(regs) && !search_exception_tables(regs->pc)) + if (!user_mode(regs) && !search_exception_tables(regs->pc)) { + up_read(&mm->mmap_sem); goto no_context; + } #endif } -- 2.7.4 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=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH,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 94EA9C28CC0 for ; 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Wed, 29 May 2019 05:34:42 -0700 (PDT) From: Anshuman Khandual To: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/4] arm64/mm: Drop mmap_sem before calling __do_kernel_fault() Date: Wed, 29 May 2019 18:04:42 +0530 Message-Id: <1559133285-27986-2-git-send-email-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> References: <1559133285-27986-1-git-send-email-anshuman.khandual@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190529_053446_186213_A3451B29 X-CRM114-Status: GOOD ( 13.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Anshuman Khandual , Catalin Marinas , Will Deacon , James Morse , Andrey Konovalov MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org There is an inconsistency between down_read_trylock() success and failure paths while dealing with kernel access for non exception table areas where it calls __do_kernel_fault(). In case of failure it just bails out without holding mmap_sem but when it succeeds it does so while holding mmap_sem. Fix this inconsistency by just dropping mmap_sem in success path as well. __do_kernel_fault() calls die_kernel_fault() which then calls show_pte(). show_pte() in this path might become bit more unreliable without holding mmap_sem. But there are already instances [1] in do_page_fault() where die_kernel_fault() gets called without holding mmap_sem. show_pte() can be made more robust independently but in a later patch. [1] Conditional block for (is_ttbr0_addr && is_el1_permission_fault) Signed-off-by: Anshuman Khandual Cc: Catalin Marinas Cc: Will Deacon Cc: Mark Rutland Cc: James Morse Cc: Andrey Konovalov --- arch/arm64/mm/fault.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index a30818e..dc1cf32 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -503,8 +503,10 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, */ might_sleep(); #ifdef CONFIG_DEBUG_VM - if (!user_mode(regs) && !search_exception_tables(regs->pc)) + if (!user_mode(regs) && !search_exception_tables(regs->pc)) { + up_read(&mm->mmap_sem); goto no_context; + } #endif } -- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel