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=-5.3 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,USER_AGENT_SANE_1 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 457B5C433FF for ; Wed, 14 Aug 2019 16:03:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 16E29208C2 for ; Wed, 14 Aug 2019 16:03:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565798584; bh=Zz23p4lEGrVE32BuJjlO5gztoMONPBASem+J1rR05U4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rO4/bRVNtWC5NdN4V/tOwttQr7M8fTs3p7o1YDUjzkADwmto5AwRKw8ID9Bloacf0 taWyY0/quNK0udmokxcBUS7I8bhAgX+fg+vLAAA/otkNzhVWp/YSBM742hg+UcaRdG GMubcg/MBPskyHujNHVJ0qhJq+h9PtXsacNNT1ts= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726166AbfHNQDD (ORCPT ); Wed, 14 Aug 2019 12:03:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:58598 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725828AbfHNQDD (ORCPT ); Wed, 14 Aug 2019 12:03:03 -0400 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 D1D6A2083B; Wed, 14 Aug 2019 16:03:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565798582; bh=Zz23p4lEGrVE32BuJjlO5gztoMONPBASem+J1rR05U4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qFNO82ppI7D0tq92TaZmyKhowzFVhpa9lbf3L8iaBNFasSg4rYnBTJA0BoxhjC1tq daQ9bBG6xAUX2ER08ZRRUn48zL3jk7BH3rtFOB6QFD/RGHV0MoeMZoFyRnxqLa2T8I Sgvoasb95luMFeiomCXzaIbpp87UxMZ1N+74ONjQ= Date: Wed, 14 Aug 2019 18:02:59 +0200 From: Greg KH To: Monthero Ronald Cc: viro@zeniv.linux.org.uk, stable@vger.kernel.org Subject: Re: [PATCH] fs: buffer: Check to avoid NULL pointer dereference of returned buffer_head for a private page Message-ID: <20190814160259.GA11018@kroah.com> References: <1565795351-10543-1-git-send-email-rhmcruiser@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1565795351-10543-1-git-send-email-rhmcruiser@gmail.com> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, Aug 15, 2019 at 01:09:11AM +1000, Monthero Ronald wrote: > The patch checks for this condition of NULL pointer for the buffer_head returned from page_buffers() > and also a check placed within the list traversal loop for next buffer_head structs. > > crash scenario: > The buffer_head returned from page_buffers() is not checked in block_invalidatepage_range function. > The struct buffer_head* pointer returned by page_buffers(page) was 0x0, although this page had its > private flag PG_private bit set and was expected to have buffer_head structs attached.The NULL pointer > buffer_head was dereferenced in block_invalidatepage_range function at bh->b_size, where bh returned by > page_buffers(page) was 0x0. > > The stack frames were truncate_inode_page() => do_invalidatepage_range() => xfs_vm_invalidatepage() => > [exception RIP: block_invalidatepage_range+132] > > The inode for truncate in this case was valid and had proper inode.i_state = 0x20 - FREEING and had > a valid mapped address space to xfs. And the struct page in context of block_invalidatepage_range() > had its page flag PG_private set but the page.private was 0x0. So page_buffers(page) returned 0x0 > and hence the crash. > This patch performs NULL pointer check for returned buffer_head. Applies to 3.16 and later kernels. > > Signed-off-by: Monthero Ronald > --- > fs/buffer.c | 2 ++ > 1 file changed, 2 insertions(+) This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.