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Wed, 1 Dec 2021 06:22:15 GMT Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9A7DB6E054; Wed, 1 Dec 2021 06:22:15 +0000 (GMT) Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6C9A16E052; Wed, 1 Dec 2021 06:22:10 +0000 (GMT) Received: from skywalker.linux.ibm.com (unknown [9.43.38.73]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 1 Dec 2021 06:22:09 +0000 (GMT) X-Mailer: emacs 28.0.50 (via feedmail 11-beta-1 I) From: "Aneesh Kumar K.V" To: Andrew Morton Cc: linux-mm@kvack.org, Ben Widawsky , Dave Hansen , Feng Tang , Michal Hocko , Andrea Arcangeli , Mel Gorman , Mike Kravetz , Randy Dunlap , Vlastimil Babka , Andi Kleen , Dan Williams , Huang Ying , linux-api@vger.kernel.org Subject: Re: [PATCH v5 2/3] mm/mempolicy: add set_mempolicy_home_node syscall In-Reply-To: <20211130190028.6644054bc7142af36ef5c648@linux-foundation.org> References: <20211116064238.727454-1-aneesh.kumar@linux.ibm.com> <20211116064238.727454-3-aneesh.kumar@linux.ibm.com> <20211129140215.11b7cf9f1034a7fe7017768c@linux-foundation.org> <87wnkqaujt.fsf@linux.ibm.com> <20211130190028.6644054bc7142af36ef5c648@linux-foundation.org> Date: Wed, 01 Dec 2021 11:52:08 +0530 Message-ID: <87r1awc0a7.fsf@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: UcOHq32OOeGqmNWdexe8uvVDdw-l_AHv X-Proofpoint-GUID: BHEz3vFUC4OE8XTXBNGuBLyD2SuxBoIu X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.0.607.475 definitions=2021-11-30_10,2021-11-28_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 mlxlogscore=999 priorityscore=1501 impostorscore=0 lowpriorityscore=0 adultscore=0 spamscore=0 malwarescore=0 suspectscore=0 bulkscore=0 phishscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2112010034 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 63214D0000A6 X-Stat-Signature: w7aonm6qmbuohaxamshs6ogagc5jb3rr Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=CL4fIp14; spf=pass (imf20.hostedemail.com: domain of aneesh.kumar@linux.ibm.com designates 148.163.156.1 as permitted sender) smtp.mailfrom=aneesh.kumar@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-HE-Tag: 1638339743-375547 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Andrew Morton writes: > On Tue, 30 Nov 2021 14:29:02 +0530 "Aneesh Kumar K.V" wrote: > >> > What's the thinking here? The node can later be offlined and the >> > kernel takes no action to reset home nodes, so why not permit setting a >> > presently-offline node as the home node? Checking here seems rather >> > arbitrary? >> >> The node online check was needed to avoid accessing >> uninitialised pgdat structure. Such an access can result in >> below crash > > Oh. This is unobvious from reading the code. Which calls for a > comment, no? updated @@ -1497,6 +1498,10 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le if (flags != 0) return -EINVAL; + /* + * Check home_node is online to avoid accessing uninitialized + * NODE_DATA. + */ if (home_node >= MAX_NUMNODES || !node_online(home_node)) return -EINVAL;