From patchwork Mon Jan 23 18:23:08 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 92266 Delivered-To: patch@linaro.org Received: by 10.140.20.99 with SMTP id 90csp1353610qgi; Mon, 23 Jan 2017 10:24:12 -0800 (PST) X-Received: by 10.99.139.68 with SMTP id j65mr33989583pge.64.1485195852566; Mon, 23 Jan 2017 10:24:12 -0800 (PST) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id t186si16364194pgd.213.2017.01.23.10.24.12; Mon, 23 Jan 2017 10:24:12 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750756AbdAWSYL (ORCPT + 3 others); Mon, 23 Jan 2017 13:24:11 -0500 Received: from foss.arm.com ([217.140.101.70]:51802 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750705AbdAWSYL (ORCPT ); Mon, 23 Jan 2017 13:24:11 -0500 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 DAEB8AD7; Mon, 23 Jan 2017 10:24:10 -0800 (PST) Received: from leverpostej.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 6AEB53F3D6; Mon, 23 Jan 2017 10:24:10 -0800 (PST) From: Mark Rutland To: stable@vger.kernel.org Subject: [PATCH v3.12.y] arm64: avoid returning from bad_mode Date: Mon, 23 Jan 2017 18:23:08 +0000 Message-Id: <1485195788-22822-1-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org commit 7d9e8f71b989230bc613d121ca38507d34ada849 upstream. Generally, taking an unexpected exception should be a fatal event, and bad_mode is intended to cater for this. However, it should be possible to contain unexpected synchronous exceptions from EL0 without bringing the kernel down, by sending a SIGILL to the task. We tried to apply this approach in commit 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0"), by sending a signal for any bad_mode call resulting from an EL0 exception. However, this also applies to other unexpected exceptions, such as SError and FIQ. The entry paths for these exceptions branch to bad_mode without configuring the link register, and have no kernel_exit. Thus, if we take one of these exceptions from EL0, bad_mode will eventually return to the original user link register value. This patch fixes this by introducing a new bad_el0_sync handler to cater for the recoverable case, and restoring bad_mode to its original state, whereby it calls panic() and never returns. The recoverable case branches to bad_el0_sync with a bl, and returns to userspace via the usual ret_to_user mechanism. Signed-off-by: Mark Rutland Fixes: 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0") Reported-by: Mark Salter Cc: Will Deacon Cc: stable@vger.kernel.org Signed-off-by: Catalin Marinas --- arch/arm64/kernel/entry.S | 2 +- arch/arm64/kernel/traps.c | 25 +++++++++++++++++++++---- 2 files changed, 22 insertions(+), 5 deletions(-) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 028a1b9..c405e24 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -493,7 +493,7 @@ el0_inv: mov x0, sp mov x1, #BAD_SYNC mrs x2, esr_el1 - b bad_mode + b bad_el0_sync ENDPROC(el0_sync) .align 6 diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 7ffaddd..7d1f6c5 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -306,16 +306,33 @@ asmlinkage long do_ni_syscall(struct pt_regs *regs) } /* - * bad_mode handles the impossible case in the exception vector. + * bad_mode handles the impossible case in the exception vector. This is always + * fatal. */ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) { - siginfo_t info; - void __user *pc = (void __user *)instruction_pointer(regs); console_verbose(); pr_crit("Bad mode in %s handler detected, code 0x%08x\n", handler[reason], esr); + + die("Oops - bad mode", regs, 0); + local_irq_disable(); + panic("bad mode"); +} + +/* + * bad_el0_sync handles unexpected, but potentially recoverable synchronous + * exceptions taken from EL0. Unlike bad_mode, this returns. + */ +asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr) +{ + siginfo_t info; + void __user *pc = (void __user *)instruction_pointer(regs); + console_verbose(); + + pr_crit("Bad EL0 synchronous exception detected on CPU%d, code 0x%08x\n", + smp_processor_id(), esr); __show_regs(regs); info.si_signo = SIGILL; @@ -323,7 +340,7 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) info.si_code = ILL_ILLOPC; info.si_addr = pc; - arm64_notify_die("Oops - bad mode", regs, &info, 0); + force_sig_info(info.si_signo, &info, current); } void __pte_error(const char *file, int line, unsigned long val)