From patchwork Mon Jan 9 17:48:00 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 13094049 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7DB71C5479D for ; Mon, 9 Jan 2023 17:54:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=EjhEcytgZuv+iS0E1dSvW6ExF28BJM4jDPE/XwbI/hI=; b=0qe6/qM2MSHZ6Y dv5xPOFZtZBlP3YJbHib8uLHiP4MEZDMz0YtLc5zWOpe3vEjvrJgUmaG5f3MYX7ggeUy8sKzzzIDa UEzQBGaImso8Eq0N79+KBp7xpfkG0o5dvp9h3kMzuJFfLvFOgo1OejfFIZn0PXzmKVUtVv9UGvCnb hgDbG97jqX6tRM82C11UiH4vCrywPcKQYa0WaSCGLd5dyh+u/shbbIFudLarrodaixpX2wWhGan/N 8GPFpVeIkaNDmCxyzH8C0orkb0U4vv/JBnJ1hFZ27Nb4tMssnwNw0Qv3SF4U7NLf1TAsEPs1lfh1L uY1v31H4MVcOptjRcU5g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pEwKP-0032PI-Rq; Mon, 09 Jan 2023 17:52:58 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pEwFs-00306K-5J for linux-arm-kernel@lists.infradead.org; Mon, 09 Jan 2023 17:48:17 +0000 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 3432A61295; Mon, 9 Jan 2023 17:48:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 808CFC433F0; Mon, 9 Jan 2023 17:48:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1673286492; bh=wJHQcoruZ5sn0xjNYyGtLPmw6+8llRPdoaN3bIGrJjo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kLTqdVikeN6QwCa0bqpsrMyIgrNoTt/XgJT3ikqNwCWz/bHak+ciQXwu1z+Yzk8Ff 1zDfTC9FrYRZxH20zCN54E9FtUhbLLsA4xHUonJTEZXL77Gaqgbs/P9ovTlR0RxfIq /FMbwfAEtqKj2iwJ1VsUiYSdT8xW9zJZygnNaXWPRyr98WogbFASsew9btS+1abDmn JFk3RJ2Vpxn1wJRY7WA6Q7J9CpcJt3/qe5J/My7GmiLHaw09QQYnDHwjji7CW8UGkY 4+VOamC7RbAtkpFZcKZBLKoUO/kbPq68qQBmL4huc7sWzIvcv3957Dmj7/aX4eaL+X mwVPrny3gq3tg== From: Ard Biesheuvel To: linux-arm-kernel@lists.infradead.org Cc: will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, Ard Biesheuvel , Sami Tolvanen , Kees Cook Subject: [PATCH v2 2/2] arm64: Stash shadow stack pointer in the task struct on interrupt Date: Mon, 9 Jan 2023 18:48:00 +0100 Message-Id: <20230109174800.3286265-3-ardb@kernel.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230109174800.3286265-1-ardb@kernel.org> References: <20230109174800.3286265-1-ardb@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2053; i=ardb@kernel.org; h=from:subject; bh=wJHQcoruZ5sn0xjNYyGtLPmw6+8llRPdoaN3bIGrJjo=; b=owEB7QES/pANAwAKAcNPIjmS2Y8kAcsmYgBjvFNPKWJUWx27MHGT2IueUCSIqH3xyQiym/SngNzL b1+2fweJAbMEAAEKAB0WIQT72WJ8QGnJQhU3VynDTyI5ktmPJAUCY7xTTwAKCRDDTyI5ktmPJGZqC/ 0YaXA4ix2I3CbwZaJCNfpmV4yOZ+MFluiU71sNlRK3Jfii2Uy0Sq9BNUHFNU2EHPTCTWR0Gxyfq6o1 sqlQIfcFo+BUU5z3Aos7n79nw17MpM9DWJMI9uCHQUQvXAiae7tRQVfBnZtATlVi0TbwXWpmJ0h65y +VsvHjj5fn23w+v17QJbbQgkTagI9tzhL13Pz3TflTNPU7y0q1s7SPT9La8zAJOhTkfsQ6OQ/x1ZjX jrfy416Lu4I2GKs6xjzSC0zwJ5Ih+9SZ9MEUmfsHNEb2WPeeNhLLNuxAA+4ctgFqt2WUv0VTzRDtzr dggwHh70WtuNxSaQcurtewp0bXBmj/IQHU/9Lk0zdqam+6fC96qcqcqZ0xps5flE1yXCTiBa7J/uvH tOdB64lmKBAB9n7tM/vmVOBiW7qS86XhEOngzl8KfGP372p+QwF8IPg8DXNL/IqdYcA0Ry4DjXG5k1 vii9feuOKXYujF5Wq/FJOBLfPuMRobVQwqWdsDqq0esgk= X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230109_094816_456799_F8D8D3B5 X-CRM114-Status: GOOD ( 13.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 Acked-by: Mark Rutland Reviewed-by: Kees Cook --- arch/arm64/kernel/entry.S | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 546f7773238ea45d..80d763e165fc5856 100644 --- 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)