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 C1ADCC433EF for ; Tue, 26 Apr 2022 04:20:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243278AbiDZEXU (ORCPT ); Tue, 26 Apr 2022 00:23:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243176AbiDZEXQ (ORCPT ); Tue, 26 Apr 2022 00:23:16 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D4E9AB3E for ; Mon, 25 Apr 2022 21:20:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1650946807; x=1682482807; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=wRcUZ8Y/n8pAL9A/qgitFb6rt9lmE3TkOX7+yyhh2MA=; b=Ho8FQcN+GAr80CLBi31kfxSsC70MTRnQM8yryjMTNcCRBqC6MK7+Tt8h K9wYuWuI7O0Z8PnSDGL2EF2rECpu/vKXPXrOafXNiZeNbg7fAppLvbGTW e/jIO5AKE/ElaIK0+AdiTSOdxiI4BJWsJOiF8ZDinAjN9LjbWjdVKCMuv Dwty1MEnV3jHm0av1Tkm+Fy+e8oCm3KNNGcV/246miAvLkIO3kL2z521+ nXNYkxdEUmoss5tCYhOP1QzvIbhf9Egju9zCUtFSM4l8dsQSN7+tYzyJm qs9a3l+Ufe27bce2SrUvSuuU6EBHUbl15HfSGaKoQr/xWQ9LO+5H8XDts Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10328"; a="264967306" X-IronPort-AV: E=Sophos;i="5.90,290,1643702400"; d="scan'208";a="264967306" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2022 21:20:06 -0700 X-IronPort-AV: E=Sophos;i="5.90,290,1643702400"; d="scan'208";a="730055827" Received: from fyu1.sc.intel.com ([172.25.103.126]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2022 21:20:06 -0700 Date: Mon, 25 Apr 2022 21:20:36 -0700 From: Fenghua Yu To: Jean-Philippe Brucker Cc: Jacob Pan , Dave Hansen , Tony Luck , Ashok Raj , Ravi V Shankar , Peter Zijlstra , robin.murphy@arm.com, Dave Hansen , x86 , linux-kernel , iommu , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Josh Poimboeuf , zhangfei.gao@linaro.org, Thomas Gleixner , will@kernel.org Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit Message-ID: References: <76ec6342-0d7c-7c7b-c132-2892e4048fa1@intel.com> <20220425083444.00af5674@jacob-builder> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Jean and Zhangfei, On Mon, Apr 25, 2022 at 05:13:02PM +0100, Jean-Philippe Brucker wrote: > Could we move mm_pasid_drop() to __mmdrop() instead of __mmput()? For Arm > we do need to hold the mm_count until unbind(), and mmgrab()/mmdrop() is > also part of Lu's rework [1]. Is this a right fix for the issue? Could you please test it on ARM? I don't have an ARM machine. Thanks. -Fenghua >From 84aa68f6174439d863c40cdc2db0e1b89d620dd0 Mon Sep 17 00:00:00 2001 From: Fenghua Yu Date: Fri, 15 Apr 2022 00:51:33 -0700 Subject: [PATCH] iommu/sva: Fix PASID use-after-free issue A PASID might be still used on ARM after it is freed in __mmput(). process: open()->sva_bind()->ioasid_alloc() = N; // Get PASID N for the mm exit(); exit_mm()->__mmput()->mm_pasid_drop()->mm->pasid = -1; // PASID -1 exit_files()->release(dev)->sva_unbind()->use mm->pasid; // Failure To avoid the use-after-free issue, free the PASID after no device uses it, i.e. after all devices are unbound from the mm. sva_bind()/sva_unbind() call mmgrab()/mmdrop() to track mm->mm_count. __mmdrop() is called only after mm->mm_count is zero. So freeing the PASID in __mmdrop() guarantees the PASID is safely freed only after no device is bound to the mm. Fixes: 701fac40384f ("iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit") Reported-by: Zhangfei Gao Suggested-by: Jean-Philippe Brucker Suggested-by: Jacob Pan Signed-off-by: Fenghua Yu --- kernel/fork.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/fork.c b/kernel/fork.c index 9796897560ab..35a3beff140b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -792,6 +792,7 @@ void __mmdrop(struct mm_struct *mm) mmu_notifier_subscriptions_destroy(mm); check_mm(mm); put_user_ns(mm->user_ns); + mm_pasid_drop(mm); free_mm(mm); } EXPORT_SYMBOL_GPL(__mmdrop); @@ -1190,7 +1191,6 @@ static inline void __mmput(struct mm_struct *mm) } if (mm->binfmt) module_put(mm->binfmt->module); - mm_pasid_drop(mm); mmdrop(mm); } -- 2.32.0