From nobody Sat Feb 7 23:22:57 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 D196AEB64DC for ; Thu, 6 Jul 2023 05:50:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233109AbjGFFuQ (ORCPT ); Thu, 6 Jul 2023 01:50:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33116 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229527AbjGFFuO (ORCPT ); Thu, 6 Jul 2023 01:50:14 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69C36110 for ; Wed, 5 Jul 2023 22:50:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1688622613; x=1720158613; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=w6/BBpGC9o6TMtXs4FPV+zb5Oys3dj7edttjfM+T3Mw=; b=LSS5NONWXJKLNGkMKCuGFNZcNd8BvO9C8u7pZi8qEcS8szSFGY2lZPfl hHeJHFdikCrM++Ny+D0PhSLxoduSSzmXhqAl1NTXqFJJg9KbKekoIu+wW GO3oA7P2euTsUpj8n7dngl8HAO3UkhPTFPF0EQjNBt494mojrXzMxdr4B inY7Jdk50usDBVNtN74ZilDkHcbWqFwtqVpiZfgh2OOJzy/9AT8EXmUlW C8ku/Qj3PwP9FqWuDgiBxFVCAoNqE1Igz9VoLrHXbXsRra/vT8uIzY5Tj 3ETeUwTDh3FRq0bMQyHpadmXFbUIresocPijXhp9AXtc4J8kRYo1ivhv+ Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10762"; a="362383031" X-IronPort-AV: E=Sophos;i="6.01,185,1684825200"; d="scan'208";a="362383031" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Jul 2023 22:50:13 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10762"; a="719479867" X-IronPort-AV: E=Sophos;i="6.01,185,1684825200"; d="scan'208";a="719479867" Received: from unknown (HELO fred..) ([172.25.112.68]) by orsmga002.jf.intel.com with ESMTP; 05 Jul 2023 22:50:12 -0700 From: Xin Li To: linux-kernel@vger.kernel.org, x86@kernel.org Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, brgerst@gmail.com, ebiederm@xmission.com, xin3.li@intel.com Subject: [PATCH] x86/ia32: Do not modify the DPL bits for a null selector Date: Wed, 5 Jul 2023 22:22:31 -0700 Message-Id: <20230706052231.2183-1-xin3.li@intel.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" When a null selector is to be loaded into a segment register, reload_segments() sets its DPL bits to 3. Later when an IRET instruction loads it, it zeros the segment register. The two operations offset each other to actually effect a nop. Fix it by not modifying the DPL bits for a null selector. Signed-off-by: Xin Li --- arch/x86/kernel/signal_32.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c index 9027fc088f97..7796cf84fca2 100644 --- a/arch/x86/kernel/signal_32.c +++ b/arch/x86/kernel/signal_32.c @@ -36,22 +36,27 @@ #ifdef CONFIG_IA32_EMULATION #include =20 +static inline u16 usrseg(u16 sel) +{ + return sel <=3D 3 ? sel : sel | 3; +} + static inline void reload_segments(struct sigcontext_32 *sc) { unsigned int cur; =20 savesegment(gs, cur); - if ((sc->gs | 0x03) !=3D cur) - load_gs_index(sc->gs | 0x03); + if (usrseg(sc->gs) !=3D cur) + load_gs_index(usrseg(sc->gs)); savesegment(fs, cur); - if ((sc->fs | 0x03) !=3D cur) - loadsegment(fs, sc->fs | 0x03); + if (usrseg(sc->fs) !=3D cur) + loadsegment(fs, usrseg(sc->fs)); savesegment(ds, cur); - if ((sc->ds | 0x03) !=3D cur) - loadsegment(ds, sc->ds | 0x03); + if (usrseg(sc->ds) !=3D cur) + loadsegment(ds, usrseg(sc->ds)); savesegment(es, cur); - if ((sc->es | 0x03) !=3D cur) - loadsegment(es, sc->es | 0x03); + if (usrseg(sc->es) !=3D cur) + loadsegment(es, usrseg(sc->es)); } =20 #define sigset32_t compat_sigset_t --=20 2.34.1