From nobody Fri Nov 29 02:34:26 2024 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9D371148838; Wed, 25 Sep 2024 22:25:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.8 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727303142; cv=none; b=Mygbbv3u+1i+rTWm9hi1RFEYWpgE8mStFkQMx1O1sMObwNrDM+fhhfEfSZXp4B6qE8GebxGwiA6XfW8hfU3nfRmKmIs1MWo/xI8rnhebJAy9MGjLdzUYbtuFVYxD/eodEqAhB++H7m03FkmJmaUKGgEKbnAw5sM/pa5b4Tphj/g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727303142; c=relaxed/simple; bh=OduRHAVBGOjYFmib5cZvnd9hU/f1pWV6cNPWVVpgWck=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=je+wClwSPcYOZ+zN6doEzkFgQuz6gLDNTCnDUPOtP8PRX5NMmxHkeu51wEbVu4ABhT3YMZelaR0zN7yWfMxjLOOtB2Y4E46fnmuoiHeJuuIhIvaj/kMOKXijDbo4ZvUrEDK57MGHygGm6xMhW3Ot8oHCXcheNAc8ZCjipp8eqSU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=OQ0HeytU; arc=none smtp.client-ip=192.198.163.8 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="OQ0HeytU" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1727303141; x=1758839141; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=OduRHAVBGOjYFmib5cZvnd9hU/f1pWV6cNPWVVpgWck=; b=OQ0HeytUAPRAkjdeffHDIX3F90jCI0o918G3mqJlh5llAcZ65w24UW49 E0qr87qohfXxBaAJ4OiHcNnSl6VYPVM2aKBNqq6mAS0skJz+LK14VId9K XNjRFBTgGqY7GkFcQhxWbXmntbTi/awOW0iEuN3Y/tgGQRwYbYNqIPN7B L8mtDI5Ts1Ngb6TU4LTChB05dApls9f7SwMswBTMkj421eeewH1zbydq3 /CGnD4xnDQWNwGJYwq73sEaHE+jFWonzGnDvlX55KHSThsmCyc5qI2a5Z fKA98dVO2CpHliMB0iflrVHpgbzUycC4Da26YDWh6ubsP0h92lGdU8Rza Q==; X-CSE-ConnectionGUID: Nixj/67cQcq/p1oGcfKt+w== X-CSE-MsgGUID: gLxGSkLmRZuThyHFsXlmOw== X-IronPort-AV: E=McAfee;i="6700,10204,11206"; a="43895126" X-IronPort-AV: E=Sophos;i="6.10,258,1719903600"; d="scan'208";a="43895126" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by fmvoesa102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Sep 2024 15:25:40 -0700 X-CSE-ConnectionGUID: ylRPP6vTTViXmAkOvhxqFg== X-CSE-MsgGUID: XqEOZxuLTpWVGAux8F33RQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.10,258,1719903600"; d="scan'208";a="71929250" Received: from fecarpio-mobl.amr.corp.intel.com (HELO desk) ([10.125.147.229]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Sep 2024 15:25:39 -0700 Date: Wed, 25 Sep 2024 15:25:38 -0700 From: Pawan Gupta To: Borislav Petkov , Dave Hansen Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Robert Gill , Jari Ruusu , Brian Gerst , "Linux regression tracking (Thorsten Leemhuis)" , antonio.gomez.iglesias@linux.intel.com, daniel.sneddon@linux.intel.com, stable@vger.kernel.org Subject: [PATCH v7 1/3] x86/entry_32: Do not clobber user EFLAGS.ZF Message-ID: <20240925-fix-dosemu-vm86-v7-1-1de0daca2d42@linux.intel.com> X-Mailer: b4 0.14.1 References: <20240925-fix-dosemu-vm86-v7-0-1de0daca2d42@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240925-fix-dosemu-vm86-v7-0-1de0daca2d42@linux.intel.com> Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Opportunistic SYSEXIT executes VERW to clear CPU buffers after user EFLAGS are restored. This can clobber user EFLAGS.ZF. Move CLEAR_CPU_BUFFERS before the user EFLAGS are restored. This ensures that the user EFLAGS.ZF is not clobbered. Fixes: a0e2dab44d22 ("x86/entry_32: Add VERW just before userspace transiti= on") Reported-by: Jari Ruusu Closes: https://lore.kernel.org/lkml/yVXwe8gvgmPADpRB6lXlicS2fcHoV5OHHxyuFb= B_MEleRPD7-KhGe5VtORejtPe-KCkT8Uhcg5d7-IBw4Ojb4H7z5LQxoZylSmJ8KNL3A8o=3D@pr= otonmail.com/ Cc: stable@vger.kernel.org # 5.10+ Signed-off-by: Pawan Gupta --- arch/x86/entry/entry_32.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index d3a814efbff6..9ad6cd89b7ac 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -871,6 +871,8 @@ SYM_FUNC_START(entry_SYSENTER_32) =20 /* Now ready to switch the cr3 */ SWITCH_TO_USER_CR3 scratch_reg=3D%eax + /* Clobbers ZF */ + CLEAR_CPU_BUFFERS =20 /* * Restore all flags except IF. (We restore IF separately because @@ -881,7 +883,6 @@ SYM_FUNC_START(entry_SYSENTER_32) BUG_IF_WRONG_CR3 no_user_check=3D1 popfl popl %eax - CLEAR_CPU_BUFFERS =20 /* * Return back to the vDSO, which will pop ecx and edx. --=20 2.34.1