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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7AE81CCA47F for ; Tue, 12 Jul 2022 19:07:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235610AbiGLTHg (ORCPT ); Tue, 12 Jul 2022 15:07:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60284 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235459AbiGLTGx (ORCPT ); Tue, 12 Jul 2022 15:06:53 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BC469FB8C2; Tue, 12 Jul 2022 11:51:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B7A6861491; Tue, 12 Jul 2022 18:51:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A974FC3411C; Tue, 12 Jul 2022 18:51:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657651880; bh=shRat7IUwl93UZ/ixdmyAqfcSvEzlZjfd1rUIGGZm38=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NxSogrnFqyfqhYwsMFHJDLbiwjBQ6lbs5pX8UComBPM0pOVA349r9rzZTSNF4V3jX +pa+2pjKIUJwAADzVtGGCpNc7P7yrYo5kJGSgRoFhEWy7scENU9GhJ8fwXkIVIxwGf aCbu+xkL1jS1fVwPnhuOPvDFc0x7mXHu1Lb8MsZY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lai Jiangshan , Borislav Petkov , Thadeu Lima de Souza Cascardo Subject: [PATCH 5.18 02/61] x86/entry: Switch the stack after error_entry() returns Date: Tue, 12 Jul 2022 20:38:59 +0200 Message-Id: <20220712183237.044146273@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220712183236.931648980@linuxfoundation.org> References: <20220712183236.931648980@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan commit 520a7e80c96d655fbe4650d9cc985bd9d0443389 upstream. error_entry() calls fixup_bad_iret() before sync_regs() if it is a fault from a bad IRET, to copy pt_regs to the kernel stack. It switches to the kernel stack directly after sync_regs(). But error_entry() itself is also a function call, so it has to stash the address it is going to return to, in %r12 which is unnecessarily complicated. Move the stack switching after error_entry() and get rid of the need to handle the return address. [ bp: Massage commit message. ] Signed-off-by: Lai Jiangshan Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220503032107.680190-3-jiangshanlai@gmail.com Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/entry_64.S | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -326,6 +326,8 @@ SYM_CODE_END(ret_from_fork) .macro idtentry_body cfunc has_error_code:req call error_entry + movq %rax, %rsp /* switch to the task stack if from userspace */ + ENCODE_FRAME_POINTER UNWIND_HINT_REGS movq %rsp, %rdi /* pt_regs pointer into 1st argument*/ @@ -1003,14 +1005,10 @@ SYM_CODE_START_LOCAL(error_entry) /* We have user CR3. Change to kernel CR3. */ SWITCH_TO_KERNEL_CR3 scratch_reg=%rax + leaq 8(%rsp), %rdi /* arg0 = pt_regs pointer */ .Lerror_entry_from_usermode_after_swapgs: /* Put us onto the real thread stack. */ - popq %r12 /* save return addr in %12 */ - movq %rsp, %rdi /* arg0 = pt_regs pointer */ call sync_regs - movq %rax, %rsp /* switch stack */ - ENCODE_FRAME_POINTER - pushq %r12 RET /* @@ -1042,6 +1040,7 @@ SYM_CODE_START_LOCAL(error_entry) */ .Lerror_entry_done_lfence: FENCE_SWAPGS_KERNEL_ENTRY + leaq 8(%rsp), %rax /* return pt_regs pointer */ RET .Lbstep_iret: @@ -1062,12 +1061,9 @@ SYM_CODE_START_LOCAL(error_entry) * Pretend that the exception came from user mode: set up pt_regs * as if we faulted immediately after IRET. */ - popq %r12 /* save return addr in %12 */ - movq %rsp, %rdi /* arg0 = pt_regs pointer */ + leaq 8(%rsp), %rdi /* arg0 = pt_regs pointer */ call fixup_bad_iret - mov %rax, %rsp - ENCODE_FRAME_POINTER - pushq %r12 + mov %rax, %rdi jmp .Lerror_entry_from_usermode_after_swapgs SYM_CODE_END(error_entry)