From patchwork Tue Apr 21 01:13:51 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 227381 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7024DC54FCB for ; Tue, 21 Apr 2020 01:13:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5033721D79 for ; Tue, 21 Apr 2020 01:13:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587431634; bh=0NodWTlWfCZcGlszt6Yi/kd0x5OvcKZi5OCvXNbcLAA=; h=Date:From:To:Subject:In-Reply-To:List-ID:From; b=XykzZtA7pr+WHrfb8y6HAInhdTtfhDVTZX1yzvyrFRFHyuHWXfPPR7plK38bMCzZL IyF4tKohI/BlopvHLZVHs5uXNasruJ3lofNNXPjfJMnEGKnCbBMdkpypPWInI0N3dU LiOPI0SBKti+UySx1HIMdNFJ/DwAZRkixPON8XWI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725958AbgDUBNx (ORCPT ); Mon, 20 Apr 2020 21:13:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:35382 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726793AbgDUBNx (ORCPT ); Mon, 20 Apr 2020 21:13:53 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 750BB208E4; Tue, 21 Apr 2020 01:13:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587431632; bh=0NodWTlWfCZcGlszt6Yi/kd0x5OvcKZi5OCvXNbcLAA=; h=Date:From:To:Subject:In-Reply-To:From; b=zii0oB0oO8bzXBPUJ4gPyhDrb+TvePnVtMznkOlBjgevcOWcKGkEJsmSETf5I2cau lYp67nn9zCKe7zpwI2+Clw5g0pJJMjsoWz1m+1ZlrEAlGnyLfofmj17VGqMtG2mDuB Sb9ciGqwt0VT42duBWcHpHn+3DwrnK+G63K6K0yk= Date: Mon, 20 Apr 2020 18:13:51 -0700 From: Andrew Morton To: akpm@linux-foundation.org, jgg@mellanox.com, linux-mm@kvack.org, longpeng2@huawei.com, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, sean.j.christopherson@intel.com, stable@vger.kernel.org, torvalds@linux-foundation.org, willy@infradead.org Subject: [patch 05/15] mm/hugetlb: fix a addressing exception caused by huge_pte_offset Message-ID: <20200421011351.qwgQp5LVv%akpm@linux-foundation.org> In-Reply-To: <20200420181310.c18b3c0aa4dc5b3e5ec1be10@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Longpeng Subject: mm/hugetlb: fix a addressing exception caused by huge_pte_offset 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. Link: http://lkml.kernel.org/r/20200413010342.771-1-longpeng2@huawei.com Signed-off-by: Longpeng Reviewed-by: Mike Kravetz Reviewed-by: Jason Gunthorpe Cc: Matthew Wilcox Cc: Sean Christopherson Cc: Signed-off-by: Andrew Morton --- mm/hugetlb.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/mm/hugetlb.c~mm-hugetlb-fix-a-addressing-exception-caused-by-huge_pte_offset +++ a/mm/hugetlb.c @@ -5365,8 +5365,8 @@ pte_t *huge_pte_offset(struct mm_struct { pgd_t *pgd; p4d_t *p4d; - pud_t *pud; - pmd_t *pmd; + pud_t *pud, pud_entry; + pmd_t *pmd, pmd_entry; pgd = pgd_offset(mm, addr); if (!pgd_present(*pgd)) @@ -5376,17 +5376,19 @@ pte_t *huge_pte_offset(struct mm_struct return NULL; pud = pud_offset(p4d, addr); - if (sz != PUD_SIZE && pud_none(*pud)) + pud_entry = READ_ONCE(*pud); + if (sz != PUD_SIZE && pud_none(pud_entry)) return NULL; /* hugepage or swap? */ - if (pud_huge(*pud) || !pud_present(*pud)) + if (pud_huge(pud_entry) || !pud_present(pud_entry)) return (pte_t *)pud; pmd = pmd_offset(pud, addr); - if (sz != PMD_SIZE && pmd_none(*pmd)) + pmd_entry = READ_ONCE(*pmd); + if (sz != PMD_SIZE && pmd_none(pmd_entry)) return NULL; /* hugepage or swap? */ - if (pmd_huge(*pmd) || !pmd_present(*pmd)) + if (pmd_huge(pmd_entry) || !pmd_present(pmd_entry)) return (pte_t *)pmd; return NULL;