From mboxrd@z Thu Jan 1 00:00:00 1970 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 2431CC43603 for ; Mon, 16 Dec 2019 18:01:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F04F92072D for ; Mon, 16 Dec 2019 18:01:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576519280; bh=NhTUkNUnWlUw5sRGxbnm9ErpzftSp+1qbWU5OtIbVwg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mRFalnYYEUns0hzMTOGnE7ny/KnvpDSBGMcYSmvR0Gvqkl1OunQ4lQnZzydQMgky3 9l0lAwxNwAdNXSG53lvZS2Xaj+BHadbIlTt0UbPqysg7K7yzDSSx7mQ+I8noUU7nJ1 QXkMRiDctWEzOLuqhXUDso7iwH9b2xBbBG6SzQXw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729133AbfLPSBT (ORCPT ); Mon, 16 Dec 2019 13:01:19 -0500 Received: from mail.kernel.org ([198.145.29.99]:36186 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727351AbfLPSBS (ORCPT ); Mon, 16 Dec 2019 13:01:18 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 CB6CE20CC7; Mon, 16 Dec 2019 18:01:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576519277; bh=NhTUkNUnWlUw5sRGxbnm9ErpzftSp+1qbWU5OtIbVwg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aaDrEdYsK4xYuW87ra74wbykAyJRtctZYbRvPE6A2/M7yOBbDEPq3Z5n0UDiWJyPw 6qtakkCHZtNYJ42Fnm0w46JA0/8ZxsB2sWnhzmoP26s8Tj4alfDyptnCkdZVtRwEIZ kD1gcfLMikfheMGILAu5FHKrYjQHe/q93bjiD9Nc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Hellstrom , "Kirill A. Shutemov" , Arnd Bergmann , Matthew Wilcox , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.14 267/267] mm/memory.c: fix a huge pud insertion race during faulting Date: Mon, 16 Dec 2019 18:49:53 +0100 Message-Id: <20191216174917.502311675@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191216174848.701533383@linuxfoundation.org> References: <20191216174848.701533383@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Hellstrom [ Upstream commit 3e0a2ff638b34f322eb170b1ae4515f61cfe3b14 ] [ Upstream commit 625110b5e9dae9074d8a7e67dd07f821a053eed7 ] A huge pud page can theoretically be faulted in racing with pmd_alloc() in __handle_mm_fault(). That will lead to pmd_alloc() returning an invalid pmd pointer. Fix this by adding a pud_trans_unstable() function similar to pmd_trans_unstable() and check whether the pud is really stable before using the pmd pointer. Race: Thread 1: Thread 2: Comment create_huge_pud() Fallback - not taken. create_huge_pud() Taken. pmd_alloc() Returns an invalid pointer. This will result in user-visible huge page data corruption. Note that this was caught during a code audit rather than a real experienced problem. It looks to me like the only implementation that currently creates huge pud pagetable entries is dev_dax_huge_fault() which doesn't appear to care much about private (COW) mappings or write-tracking which is, I believe, a prerequisite for create_huge_pud() falling back on thread 1, but not in thread 2. Link: http://lkml.kernel.org/r/20191115115808.21181-2-thomas_os@shipmail.org Fixes: a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent hugepages") Signed-off-by: Thomas Hellstrom Acked-by: Kirill A. Shutemov Cc: Arnd Bergmann Cc: Matthew Wilcox Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- include/asm-generic/pgtable.h | 25 +++++++++++++++++++++++++ mm/memory.c | 6 ++++++ 2 files changed, 31 insertions(+) diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 0c21014a38f23..876826240dead 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -846,6 +846,31 @@ static inline int pud_trans_huge(pud_t pud) } #endif +/* See pmd_none_or_trans_huge_or_clear_bad for discussion. */ +static inline int pud_none_or_trans_huge_or_dev_or_clear_bad(pud_t *pud) +{ + pud_t pudval = READ_ONCE(*pud); + + if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval)) + return 1; + if (unlikely(pud_bad(pudval))) { + pud_clear_bad(pud); + return 1; + } + return 0; +} + +/* See pmd_trans_unstable for discussion. */ +static inline int pud_trans_unstable(pud_t *pud) +{ +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \ + defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) + return pud_none_or_trans_huge_or_dev_or_clear_bad(pud); +#else + return 0; +#endif +} + #ifndef pmd_read_atomic static inline pmd_t pmd_read_atomic(pmd_t *pmdp) { diff --git a/mm/memory.c b/mm/memory.c index 24963eee4fb03..174252bd87df8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4054,6 +4054,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, vmf.pud = pud_alloc(mm, p4d, address); if (!vmf.pud) return VM_FAULT_OOM; +retry_pud: if (pud_none(*vmf.pud) && __transparent_hugepage_enabled(vma)) { ret = create_huge_pud(&vmf); if (!(ret & VM_FAULT_FALLBACK)) @@ -4080,6 +4081,11 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, vmf.pmd = pmd_alloc(mm, vmf.pud, address); if (!vmf.pmd) return VM_FAULT_OOM; + + /* Huge pud page fault raced with pmd_alloc? */ + if (pud_trans_unstable(vmf.pud)) + goto retry_pud; + if (pmd_none(*vmf.pmd) && __transparent_hugepage_enabled(vma)) { ret = create_huge_pmd(&vmf); if (!(ret & VM_FAULT_FALLBACK)) -- 2.20.1