From patchwork Tue Aug 9 00:35:34 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laura Abbott X-Patchwork-Id: 9270033 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 6FF2E60754 for ; Tue, 9 Aug 2016 00:37:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 60187280DE for ; Tue, 9 Aug 2016 00:37:47 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 543A52837F; Tue, 9 Aug 2016 00:37:47 +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 E47F1280DE for ; Tue, 9 Aug 2016 00:37:46 +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 1bWv1d-0001sQ-3U; Tue, 09 Aug 2016 00:36:09 +0000 Received: from mail-qk0-f180.google.com ([209.85.220.180]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1bWv1V-0001V5-Gy for linux-arm-kernel@lists.infradead.org; Tue, 09 Aug 2016 00:36:03 +0000 Received: by mail-qk0-f180.google.com with SMTP id p186so212934666qkd.1 for ; Mon, 08 Aug 2016 17:35:40 -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=os7otF4Bf/DepytCoQxSCMfGoVYaGdOiekdhRrypaKY=; b=MmDFa7gZ2MnnJMNXY0Jt9aHBmgkhXA3Z7YBkj1DuZ7onJZpOOe1pt8+HNazUrc1uTo yB7epnNYoqNiypJ1c7Lcaq/Aq5hXwfcyOVrjzN+qG9MzLAL6X+sxO5WSs3MMtvVmmY2G 3ZwP/GAOmLrol8sLl9bJY6+bzOOpd8uJtvHp1mVPa+aFlELdxyYjp70jpPmZYYe4bXTm wtXffXDP+GVuLBAGnRAUzzPB/QCy4LPJ89CfkonIx5Hn4Q1hclAPrNfaSIri1zjx9R7Z rpbSn3Ydqy2hlNNpU7ZzpbJXSJP13V9hrgkhugUKB3HbKPvcaNyg1F4SpMtpW+g53w09 969g== X-Gm-Message-State: AEkoousl3WxdfVC2rwN+SAj5lsIApXYGrvjQyeWKkKH2ANnOk4igkLNd1Wse2rrjfVFOYgBl X-Received: by 10.55.18.9 with SMTP id c9mr30024811qkh.245.1470702939850; Mon, 08 Aug 2016 17:35:39 -0700 (PDT) Received: from labbott-redhat-machine.redhat.com ([2601:602:9800:177f::337f]) by smtp.gmail.com with ESMTPSA id w16sm19007351qta.10.2016.08.08.17.35.36 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 08 Aug 2016 17:35:38 -0700 (PDT) From: Laura Abbott To: Ard Biesheuvel , Mark Rutland , Will Deacon , Catalin Marinas Subject: [PATCHv4] arm64: Handle el1 synchronous instruction aborts cleanly Date: Mon, 8 Aug 2016 17:35:34 -0700 Message-Id: <1470702934-21226-1-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-20160808_173601_709959_7C93818E X-CRM114-Status: GOOD ( 15.73 ) 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 Signed-off-by: Laura Abbott Acked-by: Mark Rutland --- v4: Rebased to master, extra error message to indicate execution of userspace memory --- arch/arm64/kernel/entry.S | 18 ++++++++++++++++++ arch/arm64/mm/fault.c | 14 ++++++++++++-- 2 files changed, 30 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 96e4a2b..bdfadef 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 +366,22 @@ el1_sync: cmp x24, #ESR_ELx_EC_BREAKPT_CUR // debug exception in EL1 b.ge el1_dbg b el1_inv +el1_ia: + /* + * Instruction abort handling + */ + mrs x0, far_el1 + enable_dbg + // re-enable interrupts if they were enabled in the aborted context + tbnz x23, #7, 1f // PSR_I_BIT + enable_irq +1: + mov x2, sp // struct pt_regs + bl do_mem_abort + + // disable interrupts before pulling preserved data off the stack + disable_irq + kernel_exit 1 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); }