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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,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 DAB4ACA90AF for ; Wed, 13 May 2020 09:50:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8ADC2492C for ; Wed, 13 May 2020 09:50:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589363448; bh=TSdAbGoPvFw3p1tkaz4eAGaJ8MYFj3rY7vna4i8xfKk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=tntcUsWKFKkH7coo+fCt3x+Ialy/WEGkx56R7pol2ctOBcEyx/hPu+a7GjnafLJOa 3G7zwXSE86jJV5l79E2AT4Uk5LDbLvzuHbK6DNSLtcFjUJMdpD2yGpBjpEXond2mef uVGAeOP0VxtA2+sski6jmPVW+utFjJbmizkSpzts= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387556AbgEMJus (ORCPT ); Wed, 13 May 2020 05:50:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:50650 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387529AbgEMJuj (ORCPT ); Wed, 13 May 2020 05:50:39 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2E256206D6; Wed, 13 May 2020 09:50:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589363438; bh=TSdAbGoPvFw3p1tkaz4eAGaJ8MYFj3rY7vna4i8xfKk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LLPVY8Nv7/B/9E5g2JP1jLZvMQissOEwzcnqm13TAunu0+hw2iSIMRoSXbukqJRQB /mSLUUOxz7Wjyjyg7vvuyMl4HUpEMM7IrJgkijsyNuef043azOwxY6qhVmgW9BbWR3 MWbWhzx9fni2lpkssthJTDsdDCvtndYUP/uXdtAA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vince Weaver , Dave Jones , "Dr. David Alan Gilbert" , Joe Mario , Jann Horn , Linus Torvalds , Miroslav Benes , Josh Poimboeuf , Ingo Molnar , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner Subject: [PATCH 5.4 73/90] x86/entry/64: Fix unwind hints in kernel exit path Date: Wed, 13 May 2020 11:45:09 +0200 Message-Id: <20200513094416.934392058@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200513094408.810028856@linuxfoundation.org> References: <20200513094408.810028856@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Josh Poimboeuf commit 1fb143634a38095b641a3a21220774799772dc4c upstream. In swapgs_restore_regs_and_return_to_usermode, after the stack is switched to the trampoline stack, the existing UNWIND_HINT_REGS hint is no longer valid, which can result in the following ORC unwinder warning: WARNING: can't dereference registers at 000000003aeb0cdd for ip swapgs_restore_regs_and_return_to_usermode+0x93/0xa0 For full correctness, we could try to add complicated unwind hints so the unwinder could continue to find the registers, but when when it's this close to kernel exit, unwind hints aren't really needed anymore and it's fine to just use an empty hint which tells the unwinder to stop. For consistency, also move the UNWIND_HINT_EMPTY in entry_SYSCALL_64_after_hwframe to a similar location. Fixes: 3e3b9293d392 ("x86/entry/64: Return to userspace from the trampoline stack") Reported-by: Vince Weaver Reported-by: Dave Jones Reported-by: Dr. David Alan Gilbert Reported-by: Joe Mario Reported-by: Jann Horn Reported-by: Linus Torvalds Reviewed-by: Miroslav Benes Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: Andy Lutomirski Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lore.kernel.org/r/60ea8f562987ed2d9ace2977502fe481c0d7c9a0.1587808742.git.jpoimboe@redhat.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/entry_64.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -249,7 +249,6 @@ GLOBAL(entry_SYSCALL_64_after_hwframe) */ syscall_return_via_sysret: /* rcx and r11 are already restored (see code above) */ - UNWIND_HINT_EMPTY POP_REGS pop_rdi=0 skip_r11rcx=1 /* @@ -258,6 +257,7 @@ syscall_return_via_sysret: */ movq %rsp, %rdi movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp + UNWIND_HINT_EMPTY pushq RSP-RDI(%rdi) /* RSP */ pushq (%rdi) /* RDI */ @@ -637,6 +637,7 @@ GLOBAL(swapgs_restore_regs_and_return_to */ movq %rsp, %rdi movq PER_CPU_VAR(cpu_tss_rw + TSS_sp0), %rsp + UNWIND_HINT_EMPTY /* Copy the IRET frame to the trampoline stack. */ pushq 6*8(%rdi) /* SS */