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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0A56CC433EF for ; Mon, 1 Nov 2021 09:49:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E718460C41 for ; Mon, 1 Nov 2021 09:49:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234303AbhKAJwN (ORCPT ); Mon, 1 Nov 2021 05:52:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:51094 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232178AbhKAJo7 (ORCPT ); Mon, 1 Nov 2021 05:44:59 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 00624610CF; Mon, 1 Nov 2021 09:29:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1635758991; bh=7UvlIROule6v9EPflm1GUgqVwzZJsa3tNCDfBqhpas8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S2Mk/eETyAoFW6l9fVOONPL6B6+HkfcSrX0McWZWOqwtFhVTZ7owH7Z7J9oueMwgC m4G16j+7ouuqRZ5x5Vj9EUwkwpFmIxOI8Zmlyizf/QdwPU3hTzVuEt7Cfssaw2dlDl c1YAaRFpUtJpgrSxdyT2WTJVIhvOIsEz4sgoifYs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Hugh Dickins , Yang Shi , Hao Sun , syzbot+aae069be1de40fb11825@syzkaller.appspotmail.com, Matthew Wilcox , "Kirill A. Shutemov" , Song Liu , Andrea Righi , Andrew Morton , Linus Torvalds Subject: [PATCH 5.14 036/125] mm: khugepaged: skip huge page collapse for special files Date: Mon, 1 Nov 2021 10:16:49 +0100 Message-Id: <20211101082540.004331211@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211101082533.618411490@linuxfoundation.org> References: <20211101082533.618411490@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yang Shi commit a4aeaa06d45e90f9b279f0b09de84bd00006e733 upstream. The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [shy828301@gmail.com: fix vm_file check [3]] Link: https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ [1] Link: https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@google.com/ [2] Link: https://lkml.kernel.org/r/CAHbLzkqTW9U3VvTu1Ki5v_cLRC9gHW+znBukg_ycergE0JWj-A@mail.gmail.com [3] Link: https://lkml.kernel.org/r/20211027195221.3825-1-shy828301@gmail.com Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Hugh Dickins Signed-off-by: Yang Shi Reported-by: Hao Sun Reported-by: syzbot+aae069be1de40fb11825@syzkaller.appspotmail.com Cc: Matthew Wilcox Cc: Kirill A. Shutemov Cc: Song Liu Cc: Andrea Righi Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/khugepaged.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -445,22 +445,25 @@ static bool hugepage_vma_check(struct vm if (!transhuge_vma_enabled(vma, vm_flags)) return false; + if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - + vma->vm_pgoff, HPAGE_PMD_NR)) + return false; + /* Enabled via shmem mount options or sysfs settings. */ - if (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) { - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); - } + if (shmem_file(vma->vm_file)) + return shmem_huge_enabled(vma); /* THP settings require madvise. */ if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) return false; - /* Read-only file mappings need to be aligned for THP to work. */ + /* Only regular file is valid */ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && - !inode_is_open_for_write(vma->vm_file->f_inode) && (vm_flags & VM_EXEC)) { - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); + struct inode *inode = vma->vm_file->f_inode; + + return !inode_is_open_for_write(inode) && + S_ISREG(inode->i_mode); } if (!vma->anon_vma || vma->vm_ops)