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=-9.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 6BF65ECDE46 for ; Thu, 25 Oct 2018 14:16:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30ADD208A3 for ; Thu, 25 Oct 2018 14:16:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="10pBM6Lh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 30ADD208A3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729189AbeJYWsy (ORCPT ); Thu, 25 Oct 2018 18:48:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:57760 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728221AbeJYWsx (ORCPT ); Thu, 25 Oct 2018 18:48:53 -0400 Received: from sasha-vm.mshome.net (unknown [167.98.65.38]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6868120883; Thu, 25 Oct 2018 14:15:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1540476955; bh=3BUaLJ8775bHuFtNIvCd5Tc6q5iUA7+Ho/uWvQhGtgQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=10pBM6LhrGV9/OZCANRpCafUQGcY67ae3DwyIO1+k/Itp76oIEW5f2Bqp/1HIIxmr t1b/3/NOF32OeyCKdWBWPlEXWOBvkP0/oxvkWf+4uIFvS0XVgMGdZRtlvYU2NQi+uF FjylnYc3P3+kwDpYljMWW7shFGIT6rLValD6yMGU= From: Sasha Levin To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Thomas Gleixner , Peter Zijlstra , Borislav Petkov , Linus Torvalds , Ingo Molnar , Sasha Levin Subject: [PATCH AUTOSEL 4.9 62/98] x86/power: Fix some ordering bugs in __restore_processor_context() Date: Thu, 25 Oct 2018 10:13:47 -0400 Message-Id: <20181025141423.213774-62-sashal@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20181025141423.213774-1-sashal@kernel.org> References: <20181025141423.213774-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski [ Upstream commit 5b06bbcfc2c621da3009da8decb7511500c293ed ] __restore_processor_context() had a couple of ordering bugs. It restored GSBASE after calling load_gs_index(), and the latter can call into tracing code. It also tried to restore segment registers before restoring the LDT, which is straight-up wrong. Reorder the code so that we restore GSBASE, then the descriptor tables, then the segments. This fixes two bugs. First, it fixes a regression that broke resume under certain configurations due to irqflag tracing in native_load_gs_index(). Second, it fixes resume when the userspace process that initiated suspect had funny segments. The latter can be reproduced by compiling this: // SPDX-License-Identifier: GPL-2.0 /* * ldt_echo.c - Echo argv[1] while using an LDT segment */ int main(int argc, char **argv) { int ret; size_t len; char *buf; const struct user_desc desc = { .entry_number = 0, .base_addr = 0, .limit = 0xfffff, .seg_32bit = 1, .contents = 0, /* Data, grow-up */ .read_exec_only = 0, .limit_in_pages = 1, .seg_not_present = 0, .useable = 0 }; if (argc != 2) errx(1, "Usage: %s STRING", argv[0]); len = asprintf(&buf, "%s\n", argv[1]); if (len < 0) errx(1, "Out of memory"); ret = syscall(SYS_modify_ldt, 1, &desc, sizeof(desc)); if (ret < -1) errno = -ret; if (ret) err(1, "modify_ldt"); asm volatile ("movw %0, %%es" :: "rm" ((unsigned short)7)); write(1, buf, len); return 0; } and running ldt_echo >/sys/power/mem Without the fix, the latter causes a triple fault on resume. Fixes: ca37e57bbe0c ("x86/entry/64: Add missing irqflags tracing to native_load_gs_index()") Reported-by: Jarkko Nikula Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Tested-by: Jarkko Nikula Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Linus Torvalds Link: https://lkml.kernel.org/r/6b31721ea92f51ea839e79bd97ade4a75b1eeea2.1512057304.git.luto@kernel.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- arch/x86/power/cpu.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 53cace2ec0e2..73063dfed476 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -222,8 +222,20 @@ static void notrace __restore_processor_state(struct saved_context *ctxt) load_idt((const struct desc_ptr *)&ctxt->idt_limit); #endif +#ifdef CONFIG_X86_64 /* - * segment registers + * We need GSBASE restored before percpu access can work. + * percpu access can happen in exception handlers or in complicated + * helpers like load_gs_index(). + */ + wrmsrl(MSR_GS_BASE, ctxt->gs_base); +#endif + + fix_processor_context(); + + /* + * Restore segment registers. This happens after restoring the GDT + * and LDT, which happen in fix_processor_context(). */ #ifdef CONFIG_X86_32 loadsegment(es, ctxt->es); @@ -244,13 +256,14 @@ static void notrace __restore_processor_state(struct saved_context *ctxt) load_gs_index(ctxt->gs); asm volatile ("movw %0, %%ss" :: "r" (ctxt->ss)); + /* + * Restore FSBASE and user GSBASE after reloading the respective + * segment selectors. + */ wrmsrl(MSR_FS_BASE, ctxt->fs_base); - wrmsrl(MSR_GS_BASE, ctxt->gs_base); wrmsrl(MSR_KERNEL_GS_BASE, ctxt->gs_kernel_base); #endif - fix_processor_context(); - do_fpu_end(); x86_platform.restore_sched_clock_state(); mtrr_bp_restore(); -- 2.17.1