From nobody Sun Feb 8 18:44:50 2026 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 62A98C6FD1D for ; Mon, 20 Mar 2023 16:46:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231732AbjCTQqO (ORCPT ); Mon, 20 Mar 2023 12:46:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233311AbjCTQpN (ORCPT ); Mon, 20 Mar 2023 12:45:13 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6E2AA260; Mon, 20 Mar 2023 09:40:01 -0700 (PDT) Date: Mon, 20 Mar 2023 16:39:20 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1679330361; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=vVhpGGV4E0OgcgbnIV2egnjyQ1eflBcjehbPQuqlB1o=; b=BUoGqWUFgwjgLKXGfdhiwLgTiKURqMTYooMWbPe4PFQnEtRVJijyK/ATWchWzNXosF0VO4 EmBlSnipHjS/TcR+k0WUdWDBW1zDWQg9aze4/Ca51/CZ7wuheOTSuRW5vW6vsjybL8v1G/ i0oHZqCLTzpT0LjmurtxM5bt45eFcL1U2gjxG1gIOI58nbbWuh6EPKTo2aM78PaO4nEMse ItWtDR3Bq5PW0GLlGarCedKsnil+5xe2vhBkZYnPGtubgOIg7CwBbIEyca6vLg8rNtKHti EKf7HI2ro55rpwL3TS7Wz2YV/6OFsZrGC/s3krW/u6gYn3Dou0nlSdq8qr6gcg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1679330361; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=vVhpGGV4E0OgcgbnIV2egnjyQ1eflBcjehbPQuqlB1o=; b=9UqDlkiIeDYJRvjpSegZReAMx+yGzjrJdoWhUCP91kCEqLeBAFLuDvEUano7dGBR+rNN6R WcuTIXUjo2DI9ADg== From: "tip-bot2 for Mike Rapoport" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/shstk] x86/shstk: Add ARCH_SHSTK_UNLOCK Cc: Mike Rapoport , Rick Edgecombe , Dave Hansen , "Borislav Petkov (AMD)" , Kees Cook , Pengfei Xu , John Allen , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <167933036068.5837.7711056166707419991.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/shstk branch of tip: Commit-ID: d30299329def886f8bcf068da204011a08ab75f9 Gitweb: https://git.kernel.org/tip/d30299329def886f8bcf068da204011a0= 8ab75f9 Author: Mike Rapoport AuthorDate: Sat, 18 Mar 2023 17:15:34 -07:00 Committer: Dave Hansen CommitterDate: Mon, 20 Mar 2023 09:01:12 -07:00 x86/shstk: Add ARCH_SHSTK_UNLOCK Userspace loaders may lock features before a CRIU restore operation has the chance to set them to whatever state is required by the process being restored. Allow a way for CRIU to unlock features. Add it as an arch_prctl() like the other shadow stack operations, but restrict it being called by the ptrace arch_pctl() interface. [Merged into recent API changes, added commit log and docs] Signed-off-by: Mike Rapoport Signed-off-by: Rick Edgecombe Signed-off-by: Dave Hansen Reviewed-by: Borislav Petkov (AMD) Reviewed-by: Kees Cook Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook Link: https://lore.kernel.org/all/20230319001535.23210-40-rick.p.edgecombe%= 40intel.com --- Documentation/x86/shstk.rst | 4 ++++ arch/x86/include/uapi/asm/prctl.h | 1 + arch/x86/kernel/process_64.c | 1 + arch/x86/kernel/shstk.c | 9 +++++++-- 4 files changed, 13 insertions(+), 2 deletions(-) diff --git a/Documentation/x86/shstk.rst b/Documentation/x86/shstk.rst index f09afa5..f3553cc 100644 --- a/Documentation/x86/shstk.rst +++ b/Documentation/x86/shstk.rst @@ -75,6 +75,10 @@ arch_prctl(ARCH_SHSTK_LOCK, unsigned long features) are ignored. The mask is ORed with the existing value. So any feature = bits set here cannot be enabled or disabled afterwards. =20 +arch_prctl(ARCH_SHSTK_UNLOCK, unsigned long features) + Unlock features. 'features' is a mask of all features to unlock. All + bits set are processed, unset bits are ignored. Only works via ptrace. + The return values are as follows. On success, return 0. On error, errno can be:: =20 diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/= prctl.h index e314956..200efbb 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -25,6 +25,7 @@ #define ARCH_SHSTK_ENABLE 0x5001 #define ARCH_SHSTK_DISABLE 0x5002 #define ARCH_SHSTK_LOCK 0x5003 +#define ARCH_SHSTK_UNLOCK 0x5004 =20 /* ARCH_SHSTK_ features bits */ #define ARCH_SHSTK_SHSTK (1ULL << 0) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 9bbad17..69d4cca 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -835,6 +835,7 @@ long do_arch_prctl_64(struct task_struct *task, int opt= ion, unsigned long arg2) case ARCH_SHSTK_ENABLE: case ARCH_SHSTK_DISABLE: case ARCH_SHSTK_LOCK: + case ARCH_SHSTK_UNLOCK: return shstk_prctl(task, option, arg2); default: ret =3D -EINVAL; diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index ee89c42..ad336ab 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -459,9 +459,14 @@ long shstk_prctl(struct task_struct *task, int option,= unsigned long features) return 0; } =20 - /* Don't allow via ptrace */ - if (task !=3D current) + /* Only allow via ptrace */ + if (task !=3D current) { + if (option =3D=3D ARCH_SHSTK_UNLOCK && IS_ENABLED(CONFIG_CHECKPOINT_REST= ORE)) { + task->thread.features_locked &=3D ~features; + return 0; + } return -EINVAL; + } =20 /* Do not allow to change locked features */ if (features & task->thread.features_locked)