From nobody Sun Feb 8 19:55:53 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 AA7B4C00528 for ; Wed, 2 Aug 2023 22:20:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233295AbjHBWUb (ORCPT ); Wed, 2 Aug 2023 18:20:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60330 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232949AbjHBWTh (ORCPT ); Wed, 2 Aug 2023 18:19:37 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BF5B273B; Wed, 2 Aug 2023 15:19:35 -0700 (PDT) Date: Wed, 02 Aug 2023 22:19:32 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1691014773; 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=YYSeP3oTtOgkXh3frpkRHENndWycgT3hC5KKAYr/xc4=; b=aUyktOCoWVy2dkudEpDzUOpJ+B1vEhiDi51hFRuFBkXsWHTiDd3bXySxAFrU5bkZlCNWU/ otyQEf3zGG2+i582aCWTzRI6uxTbTUyLlHcLFTjTGasta7cVwiTyCwdFQbZRkmVBgYzigk 7/eljzA5aINn/TZRn/t1vSIeNaxYR/h2oxQXt893KV0poimcGKUtgQHfkUcl6TnHcPgpSB cKxi0bC3Z53hu3QuQDf0b5cEPS0HtMKQpW3Aso2Oku0xJ8iJgHk4S56AZ5/LfOi90SCbpg s/3fxW9sUO7m7E6DYIuAb/+1aTwF8KJZBATgAjPwt/7XSSp/8qGFAunOiMV6qw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1691014773; 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=YYSeP3oTtOgkXh3frpkRHENndWycgT3hC5KKAYr/xc4=; b=XPkSbV8ouVr3q++gx0Hhc3gxNZR/dzq5W6quyNcwbGnK6n50Ltt9QphxxIvmlmEMJXjPvB 4Br5odGD8qxLGkCQ== From: "tip-bot2 for Rick Edgecombe" 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: Check that SSP is aligned on sigreturn Cc: Rick Edgecombe , Dave Hansen , x86@kernel.org, linux-kernel@vger.kernel.org MIME-Version: 1.0 Message-ID: <169101477238.28540.7777670713206141397.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: b93d6c78829ad1e22486ccc93d04bf77e45597df Gitweb: https://git.kernel.org/tip/b93d6c78829ad1e22486ccc93d04bf77e= 45597df Author: Rick Edgecombe AuthorDate: Mon, 12 Jun 2023 17:10:58 -07:00 Committer: Dave Hansen CommitterDate: Wed, 02 Aug 2023 15:01:50 -07:00 x86/shstk: Check that SSP is aligned on sigreturn The shadow stack signal frame is read by the kernel on sigreturn. It relies on shadow stack memory protections to prevent forgeries of this signal frame (which included the pre-signal SSP). It also relies on the shadow stack signal frame to have bit 63 set. Since this bit would not be set via typical shadow stack operations, so the kernel can assume it was a value it placed there. However, in order to support 32 bit shadow stack, the INCSSPD instruction can increment the shadow stack by 4 bytes. In this case SSP might be pointing to a region spanning two 8 byte shadow stack frames. It could confuse the checks described above. Since the kernel only supports shadow stack in 64 bit, just check that the SSP is 8 byte aligned in the sigreturn path. Signed-off-by: Rick Edgecombe Signed-off-by: Dave Hansen Link: https://lore.kernel.org/all/20230613001108.3040476-33-rick.p.edgecomb= e%40intel.com --- arch/x86/kernel/shstk.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index f02e8ea..a8705f7 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -252,6 +252,9 @@ static int shstk_pop_sigframe(unsigned long *ssp) unsigned long token_addr; int err; =20 + if (!IS_ALIGNED(*ssp, 8)) + return -EINVAL; + err =3D get_shstk_data(&token_addr, (unsigned long __user *)*ssp); if (unlikely(err)) return err;