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Mon, 13 Apr 2020 21:49:08 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 03DLksnV086018; Mon, 13 Apr 2020 21:47:08 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userp3020.oracle.com with ESMTP id 30bqkygj2u-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Apr 2020 21:47:08 +0000 Received: from abhmp0020.oracle.com (abhmp0020.oracle.com [141.146.116.26]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 03DLl4kW001157; Mon, 13 Apr 2020 21:47:05 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 13 Apr 2020 14:47:04 -0700 Subject: Re: [PATCH v5] mm/hugetlb: fix a addressing exception caused by huge_pte_offset To: "Longpeng (Mike)" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Andrew Morton , Jason Gunthorpe , Matthew Wilcox , Sean Christopherson , stable@vger.kernel.org References: <20200413010342.771-1-longpeng2@huawei.com> From: Mike Kravetz Message-ID: <9d32dc1b-4b94-c118-64cf-5ec47ccedbc1@oracle.com> Date: Mon, 13 Apr 2020 14:47:03 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200413010342.771-1-longpeng2@huawei.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=9590 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 mlxlogscore=999 adultscore=0 mlxscore=0 phishscore=0 malwarescore=0 spamscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004130159 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9590 signatures=668686 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 adultscore=0 mlxlogscore=999 clxscore=1015 mlxscore=0 phishscore=0 suspectscore=0 lowpriorityscore=0 bulkscore=0 malwarescore=0 priorityscore=1501 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004130158 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/12/20 6:03 PM, Longpeng(Mike) wrote: > From: Longpeng > > Our machine encountered a panic(addressing exception) after run > for a long time and the calltrace is: > RIP: 0010:[] [] hugetlb_fault+0x307/0xbe0 > RSP: 0018:ffff9567fc27f808 EFLAGS: 00010286 > RAX: e800c03ff1258d48 RBX: ffffd3bb003b69c0 RCX: e800c03ff1258d48 > RDX: 17ff3fc00eda72b7 RSI: 00003ffffffff000 RDI: e800c03ff1258d48 > RBP: ffff9567fc27f8c8 R08: e800c03ff1258d48 R09: 0000000000000080 > R10: ffffaba0704c22a8 R11: 0000000000000001 R12: ffff95c87b4b60d8 > R13: 00005fff00000000 R14: 0000000000000000 R15: ffff9567face8074 > FS: 00007fe2d9ffb700(0000) GS:ffff956900e40000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffffd3bb003b69c0 CR3: 000000be67374000 CR4: 00000000003627e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > [] ? unlock_page+0x2b/0x30 > [] ? hugetlb_fault+0x222/0xbe0 > [] follow_hugetlb_page+0x175/0x540 > [] ? cpumask_next_and+0x35/0x50 > [] __get_user_pages+0x2a0/0x7e0 > [] __get_user_pages_unlocked+0x15d/0x210 > [] __gfn_to_pfn_memslot+0x3c5/0x460 [kvm] > [] try_async_pf+0x6e/0x2a0 [kvm] > [] tdp_page_fault+0x151/0x2d0 [kvm] > ... > [] kvm_arch_vcpu_ioctl_run+0x330/0x490 [kvm] > [] kvm_vcpu_ioctl+0x309/0x6d0 [kvm] > [] ? dequeue_signal+0x32/0x180 > [] ? do_sigtimedwait+0xcd/0x230 > [] do_vfs_ioctl+0x3f0/0x540 > [] SyS_ioctl+0xa1/0xc0 > [] system_call_fastpath+0x22/0x27 > > For 1G hugepages, huge_pte_offset() wants to return NULL or pudp, but it > may return a wrong 'pmdp' if there is a race. Please look at the following > code snippet: > ... > pud = pud_offset(p4d, addr); > if (sz != PUD_SIZE && pud_none(*pud)) > return NULL; > /* hugepage or swap? */ > if (pud_huge(*pud) || !pud_present(*pud)) > return (pte_t *)pud; > > pmd = pmd_offset(pud, addr); > if (sz != PMD_SIZE && pmd_none(*pmd)) > return NULL; > /* hugepage or swap? */ > if (pmd_huge(*pmd) || !pmd_present(*pmd)) > return (pte_t *)pmd; > ... > > The following sequence would trigger this bug: > 1. CPU0: sz = PUD_SIZE and *pud = 0 , continue > 1. CPU0: "pud_huge(*pud)" is false > 2. CPU1: calling hugetlb_no_page and set *pud to xxxx8e7(PRESENT) > 3. CPU0: "!pud_present(*pud)" is false, continue > 4. CPU0: pmd = pmd_offset(pud, addr) and maybe return a wrong pmdp > However, we want CPU0 to return NULL or pudp in this case. > > We must make sure there is exactly one dereference of pud and pmd. > > Cc: Mike Kravetz > Cc: Andrew Morton > Cc: Jason Gunthorpe > Cc: Matthew Wilcox > Cc: Sean Christopherson > Cc: stable@vger.kernel.org > Signed-off-by: Longpeng Thank you for continuing to work this! Reviewed-by: Mike Kravetz -- Mike Kravetz