From nobody Thu Dec 18 05:40:24 2025 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 42A5CC27C40 for ; Wed, 22 Nov 2023 21:12:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344579AbjKVVMk (ORCPT ); Wed, 22 Nov 2023 16:12:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37544 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344482AbjKVVM0 (ORCPT ); Wed, 22 Nov 2023 16:12:26 -0500 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91BD2D40; Wed, 22 Nov 2023 13:12:20 -0800 (PST) Received: by mail-pf1-x443.google.com with SMTP id d2e1a72fcca58-6c115026985so264223b3a.1; Wed, 22 Nov 2023 13:12:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1700687540; x=1701292340; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=oVrRu5wbv05JVXCiU4W4p4q4IBiu16aLNt9pxHyDOm8=; b=Jb0vDsYDRkJlIf0Tw8qaMnVNgSJz3dbYeAhXrON2LFbDOUYDthhzBWLawt8M84BrdS ohm23n5Req7+V0xKcUShqijp723+AZiSaPL9+EQ6E9QD76SrALyVO5lKiJwYIriaDphf Ik/SDLSSGOBRBTCv0Ro7TmtAgufAI8LX5n5me6lSgv55AxpieK8d7wNIRifPKZc4azTS Pnw+tmSLIZSVX0Nt70m65O1un4tTpzEwDLf/RREzYQwrioYId8mppl7tcSbszD1Mea9D k2Es6xKdz6HfTmJx2vqNYKheSrtXZPfgyF0ELKgg/Q8gyAd2GzBUiemz3hIxuNi2PGpX 1/4Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1700687540; x=1701292340; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=oVrRu5wbv05JVXCiU4W4p4q4IBiu16aLNt9pxHyDOm8=; b=aQorblcMEeQ9cTVg8UpDCvY2VQqMrPflSPcxncnaDFKg5G6tsbkKALor0ijOH/aSjI zsu55cdvOAbzc+fJ6ZUKrJmF7YNJrSJVEW37ds5WbL2VyKT6RvptCeJUJ82mlgNLoU0n w7bTLUdqtkU+N9XCMHn7VyVnSPCJsYxIWfTiyjjJJFhEMDcj5k9b7zSgTCLHvgyJNhKt zWhM92hCdhj2U7qUQ0nheheXaXM/NibxrCBxCqUCOVkedQyapuYdUunPFYaJs5hyHUWH yQ2WawqVdDgvgznAsnNmfcmPz7orqdFROfW3K1qfsQ1m6a4+dP8FL1EGmzm+ow+YOa2F oN2g== X-Gm-Message-State: AOJu0Yz3lV4pgz/DhHx4+LgBFUHPZsNc55r+oWq20/5SXRvHZ7RThHHh UHDILxyJ75yTnBu0VGtmig== X-Google-Smtp-Source: AGHT+IEhhVXk/VdCpqlemyCiB0SWUWiIBbhHHB1UaPHoDn3xJW2QhnBhVaPfSnRII43jNAanPH6BAg== X-Received: by 2002:a05:6a21:9706:b0:18a:f1f5:c4ae with SMTP id ub6-20020a056a21970600b0018af1f5c4aemr3137822pzb.42.1700687540034; Wed, 22 Nov 2023 13:12:20 -0800 (PST) Received: from fedora.mshome.net ([75.167.214.230]) by smtp.gmail.com with ESMTPSA id j18-20020a635512000000b005bdbce6818esm132136pgb.30.2023.11.22.13.12.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Nov 2023 13:12:19 -0800 (PST) From: Gregory Price X-Google-Original-From: Gregory Price To: linux-mm@kvack.org Cc: linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, arnd@arndb.de, tglx@linutronix.de, luto@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, mhocko@kernel.org, tj@kernel.org, ying.huang@intel.com, Gregory Price Subject: [RFC PATCH 05/11] mm/mempolicy: modify set_mempolicy_home_node to take a task argument Date: Wed, 22 Nov 2023 16:11:54 -0500 Message-Id: <20231122211200.31620-6-gregory.price@memverge.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20231122211200.31620-1-gregory.price@memverge.com> References: <20231122211200.31620-1-gregory.price@memverge.com> 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" To make mempolicy fetchable by external tasks, we must first change the callstack to take a task as an argument. Modify the following functions to require a task argument: set_mempolicy_home_node First we refactor set_mempolicy_home_node to __set_mempolicy_home_node which accepts a task argument, and change the syscall definition to pass in (current). The only functional change in this patch is related to the way task->mm is acquired. Originally, set_mempolicy_home_node would acquire task->mm directly via (current->mm). This is unsafe to do in a non-current context. However, utilizing get_task_mm would break the original functionality of do_get_mempolicy due to the following check in get_task_mm: if (mm) { if (task->flags & PF_KTHREAD) mm =3D NULL; else mmget(mm); } To retain the original behavior, if (task =3D=3D current) we access the task->mm directly, but if (task !=3D current) we will utilize get_task_mm to safely access the mm. We always take a reference to the mm to keep the cleanup semantics simple. Signed-off-by: Gregory Price --- mm/mempolicy.c | 62 +++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 49 insertions(+), 13 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 4519f39b1a07..540163f5d349 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1521,39 +1521,67 @@ static long kernel_mbind(unsigned long start, unsig= ned long len, return do_mbind(start, len, lmode, mode_flags, &nodes, flags); } =20 -SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned lo= ng, len, - unsigned long, home_node, unsigned long, flags) +static long __set_mempolicy_home_node(struct task_struct *task, + unsigned long start, + unsigned long len, + unsigned long home_node, + unsigned long flags) { - struct mm_struct *mm =3D current->mm; + struct mm_struct *mm; struct vm_area_struct *vma, *prev; struct mempolicy *new, *old; unsigned long end; int err =3D -ENOENT; + + /* + * Behavior when task =3D=3D current allows a task modifying itself + * to bypass the check in get_task_mm and acquire the mm directly + */ + if (task =3D=3D current) { + mm =3D task->mm; + mmget(mm); + } else + mm =3D get_task_mm(task); + + if (!mm) + return -ENODEV; + VMA_ITERATOR(vmi, mm, start); =20 start =3D untagged_addr(start); - if (start & ~PAGE_MASK) - return -EINVAL; + if (start & ~PAGE_MASK) { + err =3D -EINVAL; + goto mm_out; + } /* * flags is used for future extension if any. */ - if (flags !=3D 0) - return -EINVAL; + if (flags !=3D 0) { + err =3D -EINVAL; + goto mm_out; + } =20 /* * Check home_node is online to avoid accessing uninitialized * NODE_DATA. */ - if (home_node >=3D MAX_NUMNODES || !node_online(home_node)) - return -EINVAL; + if (home_node >=3D MAX_NUMNODES || !node_online(home_node)) { + err =3D -EINVAL; + goto mm_out; + } =20 len =3D PAGE_ALIGN(len); end =3D start + len; =20 - if (end < start) - return -EINVAL; - if (end =3D=3D start) - return 0; + if (end < start) { + err =3D -EINVAL; + goto mm_out; + } + if (end =3D=3D start) { + err =3D 0; + goto mm_out; + } + mmap_write_lock(mm); prev =3D vma_prev(&vmi); for_each_vma_range(vmi, vma, end) { @@ -1585,9 +1613,17 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned lo= ng, start, unsigned long, le break; } mmap_write_unlock(mm); +mm_out: + mmput(mm); return err; } =20 +SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned lo= ng, len, + unsigned long, home_node, unsigned long, flags) +{ + return __set_mempolicy_home_node(current, start, len, home_node, flags); +} + SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len, unsigned long, mode, const unsigned long __user *, nmask, unsigned long, maxnode, unsigned int, flags) --=20 2.39.1