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 71A73C2D0CC for ; Thu, 15 Dec 2022 14:33:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229937AbiLOOdo (ORCPT ); Thu, 15 Dec 2022 09:33:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229930AbiLOOdl (ORCPT ); Thu, 15 Dec 2022 09:33:41 -0500 Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D5EFA2E698; Thu, 15 Dec 2022 06:33:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1671114812; bh=1hQfulK9A1aJkYS8yYg0LQu+L75CXVVtpgoE15DiELU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iORaxFcbToiCyVN/grObGSxhNyr+KeMyAxdw/OH7/FO92jimdrHIj2b/CBCnC0sxX ZfzvXsOlFPGuQsYEikSAZ/XGzlYwrWYc0Xd7n1hzSPh0kOxJgQ5g9Z66A9YVnphyRq tdg0JHeqGjE7ok1NWIfL+y5nadhdbZINvpzsjB/4Fiq+8M7Sm7GPWI4ODrjBb5q/OG faQqgD9FwXWWBiEo7rE+ouPw94Sg4QUSFguEKIbGriApXVsDp+jpLcnzNY65Xh+555 Ejxt6xBDigAkGav3ycnt5R7c6BzDpYXLtl0ZP/bLprRUk4ABnwW6rlyscmoSXXx4hL fB6q7L8EWAAJg== Received: from [172.16.0.118] (192-222-180-24.qc.cable.ebox.net [192.222.180.24]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4NXvqJ1M1wzbKV; Thu, 15 Dec 2022 09:33:32 -0500 (EST) Message-ID: <72a402db-b156-74ff-2241-a018cd8ee885@efficios.com> Date: Thu, 15 Dec 2022 09:33:54 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [RFC PATCH] mm/mempolicy: Fix memory leak in set_mempolicy_home_node system call Content-Language: en-US To: Michal Hocko Cc: Andrew Morton , linux-kernel@vger.kernel.org, "Aneesh Kumar K . V" , Ben Widawsky , Dave Hansen , Feng Tang , Andrea Arcangeli , Mel Gorman , Mike Kravetz , Randy Dunlap , Vlastimil Babka , Andi Kleen , Dan Williams , Huang Ying , linux-api@vger.kernel.org, stable@vger.kernel.org References: <20221214222110.200487-1-mathieu.desnoyers@efficios.com> From: Mathieu Desnoyers In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022-12-15 02:51, Michal Hocko wrote: > On Wed 14-12-22 17:21:10, Mathieu Desnoyers wrote: >> When encountering any vma in the range with policy other than MPOL_BIND >> or MPOL_PREFERRED_MANY, an error is returned without issuing a mpol_put >> on the policy just allocated with mpol_dup(). >> >> This allows arbitrary users to leak kernel memory. >> >> Fixes: c6018b4b2549 ("mm/mempolicy: add set_mempolicy_home_node syscall") >> Signed-off-by: Mathieu Desnoyers >> Cc: Aneesh Kumar K.V >> Cc: Ben Widawsky >> Cc: Dave Hansen >> Cc: Feng Tang >> Cc: Michal Hocko >> Cc: Andrea Arcangeli >> Cc: Mel Gorman >> Cc: Mike Kravetz >> Cc: Randy Dunlap >> Cc: Vlastimil Babka >> Cc: Andi Kleen >> Cc: Dan Williams >> Cc: Huang Ying >> Cc: >> Cc: Andrew Morton >> Cc: stable@vger.kernel.org # 5.17+ > > Acked-by: Michal Hocko > Thanks for catching this! > > Btw. looking at the code again it seems rather pointless to duplicate > the policy just to throw it away anyway. A slightly bigger diff but this > looks more reasonable to me. What do you think? I can also send it as a > clean up on top of your fix. I think it would be best if this comes as a cleanup on top of my fix. The diff is larger than the minimal change needed to fix the leak in stable branches. Your approach looks fine, except for the vma_policy(vma) -> old change already spotted by Aneesh. Thanks, Mathieu > --- > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 61aa9aedb728..918cdc8a7f0c 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1489,7 +1489,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le > { > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > - struct mempolicy *new; > + struct mempolicy *new. *old; > unsigned long vmstart; > unsigned long vmend; > unsigned long end; > @@ -1521,30 +1521,28 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le > return 0; > mmap_write_lock(mm); > for_each_vma_range(vmi, vma, end) { > - vmstart = max(start, vma->vm_start); > - vmend = min(end, vma->vm_end); > - new = mpol_dup(vma_policy(vma)); > - if (IS_ERR(new)) { > - err = PTR_ERR(new); > - break; > - } > - /* > - * Only update home node if there is an existing vma policy > - */ > - if (!new) > - continue; > - > /* > * If any vma in the range got policy other than MPOL_BIND > * or MPOL_PREFERRED_MANY we return error. We don't reset > * the home node for vmas we already updated before. > */ > - if (new->mode != MPOL_BIND && new->mode != MPOL_PREFERRED_MANY) { > + old = vma_policy(vma); > + if (!old) > + continue; > + if (old->mode != MPOL_BIND && old->mode != MPOL_PREFERRED_MANY) { > err = -EOPNOTSUPP; > break; > } > > + new = mpol_dup(vma_policy(vma)); > + if (IS_ERR(new)) { > + err = PTR_ERR(new); > + break; > + } > + > new->home_node = home_node; > + vmstart = max(start, vma->vm_start); > + vmend = min(end, vma->vm_end); > err = mbind_range(mm, vmstart, vmend, new); > mpol_put(new); > if (err) -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com