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 88A03C77B75 for ; Sat, 6 May 2023 12:34:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232305AbjEFMer (ORCPT ); Sat, 6 May 2023 08:34:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232208AbjEFMeq (ORCPT ); Sat, 6 May 2023 08:34:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 11FF5156AA for ; Sat, 6 May 2023 05:34:46 -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 A394C60BA4 for ; Sat, 6 May 2023 12:34:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38C4EC433EF; Sat, 6 May 2023 12:34:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1683376485; bh=oCK2zosiK7V+lseNGVhHuyJ3LC8cIUuPvmWlIRHqfVg=; h=From:To:Cc:Subject:Date:From; b=FZVfc1s6rwgxucpKjwI7qWaDSU0d6asfum3I3BhLL8Ehj0/4Jb7eoGhhlPztdzBks QzMHhMsPvMcUiWKeroywzVP+HDL7mbJYicvNQEDjqwvZwn+G4uMyX2k7z0YO+y6dD+ FkVSe1ciJCzHqJ/AzFO+iAMyPYBEUsJCOrnhuEBMff9shId+4w++/wtHL4mxVjWcY5 SBqD4SoMzopw6oE+zWmJh+1h6aRbv16U3IWO5w+eUauHblgNnd2UIiaZbMo3JdjDSD GKQu2n6AZSJnL/oBgwM6oEOZMpCPCoyjYsLi+qHh7hyffGMoqj25QNVi0b+WzSJotX suUZKfcq/bhgg== From: Ard Biesheuvel To: stable@vger.kernel.org Cc: gregkh@linuxfoundation.org, Ard Biesheuvel Subject: [PATCH 5.10.y 1/2] arm64: Always load shadow stack pointer directly from the task struct Date: Sat, 6 May 2023 14:34:33 +0200 Message-Id: <20230506123434.63470-1-ardb@kernel.org> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2602; i=ardb@kernel.org; h=from:subject; bh=oCK2zosiK7V+lseNGVhHuyJ3LC8cIUuPvmWlIRHqfVg=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JISXMM+K3U//T6lgfZhOu6+c2bU0o+myVc+bYxn2ORqxhj ncXTA/uKGVhEONgkBVTZBGY/ffdztMTpWqdZ8nCzGFlAhnCwMUpABd5zvA/ZU5Dka3y21TVAxWB qr/lEkQNDFad3vpaubKq7rZuxpabjAw/vhy60a68+nXP8ufRYYHfNquGcOtqqJyW4fj1ofi6nwY fAA== X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org All occurrences of the scs_load macro load the value of the shadow call stack pointer from the task which is current at that point. So instead of taking a task struct register argument in the scs_load macro to specify the task struct to load from, let's always reference the current task directly. This should make it much harder to exploit any instruction sequences reloading the shadow call stack pointer register from memory. Signed-off-by: Ard Biesheuvel Acked-by: Mark Rutland Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20230109174800.3286265-2-ardb@kernel.org Signed-off-by: Catalin Marinas Signed-off-by: Ard Biesheuvel --- arch/arm64/include/asm/scs.h | 7 ++++--- arch/arm64/kernel/entry.S | 4 ++-- arch/arm64/kernel/head.S | 2 +- 3 files changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/arm64/include/asm/scs.h b/arch/arm64/include/asm/scs.h index eaa2cd92e4c10122..7155055a5bebc17d 100644 --- a/arch/arm64/include/asm/scs.h +++ b/arch/arm64/include/asm/scs.h @@ -9,15 +9,16 @@ #ifdef CONFIG_SHADOW_CALL_STACK scs_sp .req x18 - .macro scs_load tsk, tmp - ldr scs_sp, [\tsk, #TSK_TI_SCS_SP] + .macro scs_load_current + get_current_task scs_sp + ldr scs_sp, [scs_sp, #TSK_TI_SCS_SP] .endm .macro scs_save tsk, tmp str scs_sp, [\tsk, #TSK_TI_SCS_SP] .endm #else - .macro scs_load tsk, tmp + .macro scs_load_current .endm .macro scs_save tsk, tmp diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index d5bc1dbdd2fda84c..28d4cdeee5ae6083 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -221,7 +221,7 @@ alternative_else_nop_endif ptrauth_keys_install_kernel tsk, x20, x22, x23 - scs_load tsk, x20 + scs_load_current .else add x21, sp, #S_FRAME_SIZE get_current_task tsk @@ -1025,7 +1025,7 @@ SYM_FUNC_START(cpu_switch_to) msr sp_el0, x1 ptrauth_keys_install_kernel x1, x8, x9, x10 scs_save x0, x8 - scs_load x1, x8 + scs_load_current ret SYM_FUNC_END(cpu_switch_to) NOKPROBE(cpu_switch_to) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index e1c25fa3b8e6ca65..351ee64c7deb4c96 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -747,7 +747,7 @@ SYM_FUNC_START_LOCAL(__secondary_switched) ldr x2, [x0, #CPU_BOOT_TASK] cbz x2, __secondary_too_slow msr sp_el0, x2 - scs_load x2, x3 + scs_load_current mov x29, #0 mov x30, #0 -- 2.39.2