From patchwork Wed Dec 6 11:16:07 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 10095541 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 4E9AE602BF for ; Wed, 6 Dec 2017 11:16:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 42A1629CBF for ; Wed, 6 Dec 2017 11:16:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 36A0329CC6; Wed, 6 Dec 2017 11:16:40 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id BDC0529CBF for ; Wed, 6 Dec 2017 11:16:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=62+RFQrueshT3KSF00yQ6MS01socEPVkUq9bM9ghN3A=; b=GVJHa89lJ6igCJQnrfqCAh2Tyt 3ci/46w/UhLza7MbiZb+WQqcpkTsWxOPAMg7t8z0dO1Fu1YYp0pZYJ76xdbcVexo6HBp1+dQwU/WD /nIDU3qzrNirBbsQ4MLD7SnwttV2Q0yD5vjNcyXFl14DAbRrc78ONelHDDU+CDzW/gn4AWSGVX3T3 TljiRNuOdUjFo8XcDZjPy9CBVFCl/6UF9LfowsFDquRKRmUKOnEeofV1W7YD8sqC43Le5XWqzSvn9 d3hCJNXbbnH+Eq9hDDXem5THIcWCwODs6FPOeBWpdulaWKOOkkaERfwbe2hGLe1WYTijLwr/l7O0Y sg/SNJfA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eMXgs-0008TX-Ui; Wed, 06 Dec 2017 11:16:38 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eMXgo-0008Qf-I1 for linux-arm-kernel@lists.infradead.org; Wed, 06 Dec 2017 11:16:36 +0000 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 0E70C15AD; Wed, 6 Dec 2017 03:16:13 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D462D3F53E; Wed, 6 Dec 2017 03:16:12 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 70A7D1AE121C; Wed, 6 Dec 2017 11:16:18 +0000 (GMT) From: Will Deacon To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/2] arm64: SW PAN: Point saved ttbr0 at the zero page when switching to init_mm Date: Wed, 6 Dec 2017 11:16:07 +0000 Message-Id: <1512558968-28980-2-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1512558968-28980-1-git-send-email-will.deacon@arm.com> References: <1512558968-28980-1-git-send-email-will.deacon@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171206_031634_663800_B394CD84 X-CRM114-Status: GOOD ( 13.24 ) 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@arm.com, catalin.marinas@arm.com, vinmenon@codeaurora.org, Will Deacon , ard.biesheuvel@linaro.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP update_saved_ttbr0 mandates that mm->pgd is not swapper, since swapper contains kernel mappings and should never be installed into ttbr0. However, this means that callers must avoid passing the init_mm to update_saved_ttbr0 which in turn can cause the saved ttbr0 value to be out-of-date in the context of the idle thread. For example, EFI runtime services may leave the saved ttbr0 pointing at the EFI page table, and kernel threads may end up with stale references to freed page tables. This patch changes update_saved_ttbr0 so that the init_mm points the saved ttbr0 value to the empty zero page, which always exists and never contains valid translations. EFI and switch can then call into update_saved_ttbr0 unconditionally. Cc: Mark Rutland Cc: Ard Biesheuvel Cc: Vinayak Menon Reported-by: Vinayak Menon Signed-off-by: Will Deacon Reviewed-by: Catalin Marinas --- arch/arm64/include/asm/efi.h | 4 +--- arch/arm64/include/asm/mmu_context.h | 22 +++++++++++++--------- 2 files changed, 14 insertions(+), 12 deletions(-) diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h index 650344d01124..c4cd5081d78b 100644 --- a/arch/arm64/include/asm/efi.h +++ b/arch/arm64/include/asm/efi.h @@ -132,11 +132,9 @@ static inline void efi_set_pgd(struct mm_struct *mm) * Defer the switch to the current thread's TTBR0_EL1 * until uaccess_enable(). Restore the current * thread's saved ttbr0 corresponding to its active_mm - * (if different from init_mm). */ cpu_set_reserved_ttbr0(); - if (current->active_mm != &init_mm) - update_saved_ttbr0(current, current->active_mm); + update_saved_ttbr0(current, current->active_mm); } } } diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h index 3257895a9b5e..f7773f90546e 100644 --- a/arch/arm64/include/asm/mmu_context.h +++ b/arch/arm64/include/asm/mmu_context.h @@ -174,11 +174,17 @@ enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk) static inline void update_saved_ttbr0(struct task_struct *tsk, struct mm_struct *mm) { - if (system_uses_ttbr0_pan()) { - BUG_ON(mm->pgd == swapper_pg_dir); - task_thread_info(tsk)->ttbr0 = - virt_to_phys(mm->pgd) | ASID(mm) << 48; - } + u64 ttbr; + + if (!system_uses_ttbr0_pan()) + return; + + if (mm == &init_mm) + ttbr = __pa_symbol(empty_zero_page); + else + ttbr = virt_to_phys(mm->pgd) | ASID(mm) << 48; + + task_thread_info(tsk)->ttbr0 = ttbr; } #else static inline void update_saved_ttbr0(struct task_struct *tsk, @@ -214,11 +220,9 @@ switch_mm(struct mm_struct *prev, struct mm_struct *next, * Update the saved TTBR0_EL1 of the scheduled-in task as the previous * value may have not been initialised yet (activate_mm caller) or the * ASID has changed since the last run (following the context switch - * of another thread of the same process). Avoid setting the reserved - * TTBR0_EL1 to swapper_pg_dir (init_mm; e.g. via idle_task_exit). + * of another thread of the same process). */ - if (next != &init_mm) - update_saved_ttbr0(tsk, next); + update_saved_ttbr0(tsk, next); } #define deactivate_mm(tsk,mm) do { } while (0)