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 68285C7EE23 for ; Mon, 8 May 2023 10:19:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234409AbjEHKTc (ORCPT ); Mon, 8 May 2023 06:19:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234407AbjEHKTT (ORCPT ); Mon, 8 May 2023 06:19:19 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6FF3D04D for ; Mon, 8 May 2023 03:19:15 -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 4C588624B7 for ; Mon, 8 May 2023 10:19:15 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7591C433D2; Mon, 8 May 2023 10:19:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1683541154; bh=+kz6BekaqLGZBQh+Udy8F/NIPv2EBNyF4appcH4vfZ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FsaLNpRVJOrQcZxdD8f5RI7R//RvziRMd8bb1F3tJztH0LgOsJh2/CU2KpmZV4/u9 qaKXBRWoPFQe/ufxjRknp+kUb9q5yaxJmKaeBsO95yVwYc46p6WbU1LCv694oAsp4Q MJhVgcvpY6C44YJVPHR/T00DxPA92rGTrGvwo0VA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ard Biesheuvel , Kees Cook , Mark Rutland , Catalin Marinas Subject: [PATCH 6.2 023/663] arm64: Stash shadow stack pointer in the task struct on interrupt Date: Mon, 8 May 2023 11:37:29 +0200 Message-Id: <20230508094429.194391496@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230508094428.384831245@linuxfoundation.org> References: <20230508094428.384831245@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Ard Biesheuvel commit 59b37fe52f49955791a460752c37145f1afdcad1 upstream. Instead of reloading the shadow call stack pointer from the ordinary stack, which may be vulnerable to the kind of gadget based attacks shadow call stacks were designed to prevent, let's store a task's shadow call stack pointer in the task struct when switching to the shadow IRQ stack. Given that currently, the task_struct::scs_sp field is only used to preserve the shadow call stack pointer while a task is scheduled out or running in user space, reusing this field to preserve and restore it while running off the IRQ stack must be safe, as those occurrences are guaranteed to never overlap. (The stack switching logic only switches stacks when running from the task stack, and so the value being saved here always corresponds to the task mode shadow stack) While at it, fold a mov/add/mov sequence into a single add. Signed-off-by: Ard Biesheuvel Reviewed-by: Kees Cook Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20230109174800.3286265-3-ardb@kernel.org Signed-off-by: Catalin Marinas Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/entry.S | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -876,19 +876,19 @@ NOKPROBE(ret_from_fork) */ SYM_FUNC_START(call_on_irq_stack) #ifdef CONFIG_SHADOW_CALL_STACK - stp scs_sp, xzr, [sp, #-16]! + get_current_task x16 + scs_save x16 ldr_this_cpu scs_sp, irq_shadow_call_stack_ptr, x17 #endif + /* Create a frame record to save our LR and SP (implicit in FP) */ stp x29, x30, [sp, #-16]! mov x29, sp ldr_this_cpu x16, irq_stack_ptr, x17 - mov x15, #IRQ_STACK_SIZE - add x16, x16, x15 /* Move to the new stack and call the function there */ - mov sp, x16 + add sp, x16, #IRQ_STACK_SIZE blr x1 /* @@ -897,9 +897,7 @@ SYM_FUNC_START(call_on_irq_stack) */ mov sp, x29 ldp x29, x30, [sp], #16 -#ifdef CONFIG_SHADOW_CALL_STACK - ldp scs_sp, xzr, [sp], #16 -#endif + scs_load_current ret SYM_FUNC_END(call_on_irq_stack) NOKPROBE(call_on_irq_stack)