From patchwork Wed Aug 10 01:25:26 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laura Abbott X-Patchwork-Id: 9272495 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 36FA8601C2 for ; Wed, 10 Aug 2016 01:27:13 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0254226255 for ; Wed, 10 Aug 2016 01:27:13 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EAB8328358; Wed, 10 Aug 2016 01:27:12 +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,HEXHASH_WORD, RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 6E83926255 for ; Wed, 10 Aug 2016 01:27:12 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1bXIHL-0008Mv-N0; Wed, 10 Aug 2016 01:25:55 +0000 Received: from mail-qt0-f170.google.com ([209.85.216.170]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bXIHI-0008Ff-9P for linux-arm-kernel@lists.infradead.org; Wed, 10 Aug 2016 01:25:53 +0000 Received: by mail-qt0-f170.google.com with SMTP id w38so14345147qtb.0 for ; Tue, 09 Aug 2016 18:25:31 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=8dgTULDjioMnNjDQXRjBKMEgRwpc+Z2jEchmZ2r+0RA=; b=Nx20spqefI14zJ9OxJ3YIW+ZtXVpl+VSvRwt6d5apn3+IgdNwSSQQUzKcBKJly/bZ4 p8LzOmuXuQaQN6xWzDL9eR55lnsG2BpMn14BWR1aABIzlXSWB1t9yhJGITY3LawbEK1L 4tR79qkTyYj/eb6vUQ9EXHxqWnLLvfHTfZ72qdxIP4PumBT7khVAayqeHBdKaLvyxMJQ 5oIEuwdJ9kEzNcd+qPXqzyHl8SxCHWvy9krvB73Z3WlN2EW0V9AMr+IIiFtVm0FPQUE9 gdd+c0MOdB/MF9t0C02LLXQYDxVpenl2aD1GMVcNlmcRzIX0h2EaXGEWIvBeQmpfKkXu AfjA== X-Gm-Message-State: AEkoouuDMgWkeHc82QIhqDoSm68hW1HKBcxeFed/6jnH/rAUhuuMFz8cCsTwltikusM8b5fx X-Received: by 10.200.46.216 with SMTP id i24mr1529242qta.79.1470792330840; Tue, 09 Aug 2016 18:25:30 -0700 (PDT) Received: from labbott-redhat-machine.redhat.com ([2601:602:9800:177f::337f]) by smtp.gmail.com with ESMTPSA id 55sm22003056qtm.36.2016.08.09.18.25.28 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Aug 2016 18:25:29 -0700 (PDT) From: Laura Abbott To: Ard Biesheuvel , Mark Rutland , Will Deacon , Catalin Marinas Subject: [PATCHv5] arm64: Handle el1 synchronous instruction aborts cleanly Date: Tue, 9 Aug 2016 18:25:26 -0700 Message-Id: <1470792326-565-1-git-send-email-labbott@redhat.com> X-Mailer: git-send-email 2.7.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20160809_182552_450470_DFAE120B X-CRM114-Status: GOOD ( 16.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Laura Abbott , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.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 Executing from a non-executable area gives an ugly message: lkdtm: Performing direct entry EXEC_RODATA lkdtm: attempting ok execution at ffff0000084c0e08 lkdtm: attempting bad execution at ffff000008880700 Bad mode in Synchronous Abort handler detected on CPU2, code 0x8400000e -- IABT (current EL) CPU: 2 PID: 998 Comm: sh Not tainted 4.7.0-rc2+ #13 Hardware name: linux,dummy-virt (DT) task: ffff800077e35780 ti: ffff800077970000 task.ti: ffff800077970000 PC is at lkdtm_rodata_do_nothing+0x0/0x8 LR is at execute_location+0x74/0x88 The 'IABT (current EL)' indicates the error but it's a bit cryptic without knowledge of the ARM ARM. There is also no indication of the specific address which triggered the fault. The increase in kernel page permissions makes hitting this case more likely as well. Handling the case in the vectors gives a much more familiar looking error message: lkdtm: Performing direct entry EXEC_RODATA lkdtm: attempting ok execution at ffff0000084c0840 lkdtm: attempting bad execution at ffff000008880680 Unable to handle kernel paging request at virtual address ffff000008880680 pgd = ffff8000089b2000 [ffff000008880680] *pgd=00000000489b4003, *pud=0000000048904003, *pmd=0000000000000000 Internal error: Oops: 8400000e [#1] PREEMPT SMP Modules linked in: CPU: 1 PID: 997 Comm: sh Not tainted 4.7.0-rc1+ #24 Hardware name: linux,dummy-virt (DT) task: ffff800077f9f080 ti: ffff800008a1c000 task.ti: ffff800008a1c000 PC is at lkdtm_rodata_do_nothing+0x0/0x8 LR is at execute_location+0x74/0x88 Acked-by: Mark Rutland Signed-off-by: Laura Abbott --- v5: Fall through to data abort case since the code is now the same --- arch/arm64/kernel/entry.S | 7 +++++++ arch/arm64/mm/fault.c | 14 ++++++++++++-- 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 96e4a2b..441420c 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -353,6 +353,8 @@ el1_sync: lsr x24, x1, #ESR_ELx_EC_SHIFT // exception class cmp x24, #ESR_ELx_EC_DABT_CUR // data abort in EL1 b.eq el1_da + cmp x24, #ESR_ELx_EC_IABT_CUR // instruction abort in EL1 + b.eq el1_ia cmp x24, #ESR_ELx_EC_SYS64 // configurable trap b.eq el1_undef cmp x24, #ESR_ELx_EC_SP_ALIGN // stack alignment exception @@ -364,6 +366,11 @@ el1_sync: cmp x24, #ESR_ELx_EC_BREAKPT_CUR // debug exception in EL1 b.ge el1_dbg b el1_inv + +el1_ia: + /* + * Fall through to the Data abort case + */ el1_da: /* * Data abort handling diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index c8beaa0..05d2bd7 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -153,6 +153,11 @@ int ptep_set_access_flags(struct vm_area_struct *vma, } #endif +static bool is_el1_instruction_abort(unsigned int esr) +{ + return ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_CUR; +} + /* * The kernel tried to access some page that wasn't present. */ @@ -161,8 +166,9 @@ static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr, { /* * Are we prepared to handle this kernel fault? + * We are almost certainly not prepared to handle instruction faults. */ - if (fixup_exception(regs)) + if (!is_el1_instruction_abort(esr) && fixup_exception(regs)) return; /* @@ -267,7 +273,8 @@ static inline bool is_permission_fault(unsigned int esr) unsigned int ec = ESR_ELx_EC(esr); unsigned int fsc_type = esr & ESR_ELx_FSC_TYPE; - return (ec == ESR_ELx_EC_DABT_CUR && fsc_type == ESR_ELx_FSC_PERM); + return (ec == ESR_ELx_EC_DABT_CUR && fsc_type == ESR_ELx_FSC_PERM) || + (ec == ESR_ELx_EC_IABT_CUR && fsc_type == ESR_ELx_FSC_PERM); } static bool is_el0_instruction_abort(unsigned int esr) @@ -312,6 +319,9 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, if (regs->orig_addr_limit == KERNEL_DS) die("Accessing user space memory with fs=KERNEL_DS", regs, esr); + if (is_el1_instruction_abort(esr)) + die("Attempting to execute userspace memory", regs, esr); + if (!search_exception_tables(regs->pc)) die("Accessing user space memory outside uaccess.h routines", regs, esr); }