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Fri, 28 Aug 2020 14:46:34 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 07SEewel008297; Fri, 28 Aug 2020 14:46:33 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 333r9prjfp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 28 Aug 2020 14:46:33 +0000 Received: from abhmp0004.oracle.com (abhmp0004.oracle.com [141.146.116.10]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 07SEkVCE008111; Fri, 28 Aug 2020 14:46:32 GMT Received: from [192.168.2.112] (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 28 Aug 2020 07:46:31 -0700 Subject: Re: [PATCH v2] mm/hugetlb: Fix a race between hugetlb sysctl handlers To: Muchun Song , akpm@linux-foundation.org Cc: ak@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200828031146.43035-1-songmuchun@bytedance.com> From: Mike Kravetz Message-ID: <3841cb84-9d0b-3327-16fe-e3ea45245fb5@oracle.com> Date: Fri, 28 Aug 2020 07:46:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200828031146.43035-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9726 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 bulkscore=0 adultscore=0 spamscore=0 mlxlogscore=999 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008280113 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9726 signatures=668679 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 impostorscore=0 mlxlogscore=999 suspectscore=0 phishscore=0 malwarescore=0 spamscore=0 priorityscore=1501 clxscore=1015 mlxscore=0 lowpriorityscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2008280113 X-Rspamd-Queue-Id: 46DC5180F8B82 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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: On 8/27/20 8:11 PM, Muchun Song wrote: > There is a race between the assignment of `table->data` and write value > to the pointer of `table->data` in the __do_proc_doulongvec_minmax() on > the other thread. > > CPU0: CPU1: > proc_sys_write > hugetlb_sysctl_handler proc_sys_call_handler > hugetlb_sysctl_handler_common hugetlb_sysctl_handler > table->data = &tmp; hugetlb_sysctl_handler_common > table->data = &tmp; > proc_doulongvec_minmax > do_proc_doulongvec_minmax sysctl_head_finish > __do_proc_doulongvec_minmax unuse_table > i = table->data; > *i = val; // corrupt CPU1's stack > > Fix this by duplicating the `table`, and only update the duplicate of > it. And introduce a helper of proc_hugetlb_doulongvec_minmax() to > simplify the code. > > The following oops was seen: > > BUG: kernel NULL pointer dereference, address: 0000000000000000 > #PF: supervisor instruction fetch in kernel mode > #PF: error_code(0x0010) - not-present page > Code: Bad RIP value. > ... > Call Trace: > ? set_max_huge_pages+0x3da/0x4f0 > ? alloc_pool_huge_page+0x150/0x150 > ? proc_doulongvec_minmax+0x46/0x60 > ? hugetlb_sysctl_handler_common+0x1c7/0x200 > ? nr_hugepages_store+0x20/0x20 > ? copy_fd_bitmaps+0x170/0x170 > ? hugetlb_sysctl_handler+0x1e/0x20 > ? proc_sys_call_handler+0x2f1/0x300 > ? unregister_sysctl_table+0xb0/0xb0 > ? __fd_install+0x78/0x100 > ? proc_sys_write+0x14/0x20 > ? __vfs_write+0x4d/0x90 > ? vfs_write+0xef/0x240 > ? ksys_write+0xc0/0x160 > ? __ia32_sys_read+0x50/0x50 > ? __close_fd+0x129/0x150 > ? __x64_sys_write+0x43/0x50 > ? do_syscall_64+0x6c/0x200 > ? entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Fixes: e5ff215941d5 ("hugetlb: multiple hstates for multiple page sizes") > Signed-off-by: Muchun Song Thank you! Reviewed-by: Mike Kravetz -- Mike Kravetz