From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:36574 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754049AbdGYTZK (ORCPT ); Tue, 25 Jul 2017 15:25:10 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Kara Subject: [PATCH 4.12 154/196] udf: Fix races with i_size changes during readpage Date: Tue, 25 Jul 2017 12:22:33 -0700 Message-Id: <20170725192053.525678799@linuxfoundation.org> In-Reply-To: <20170725192046.422343510@linuxfoundation.org> References: <20170725192046.422343510@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jan Kara commit 9795e0e8ac0d6a3ee092f1b555b284b57feef99e upstream. __udf_adinicb_readpage() uses i_size several times. When truncate changes i_size while the function is running, it can observe several different values and thus e.g. expose uninitialized parts of page to userspace. Also use i_size_read() in the function since it does not hold inode_lock. Since i_size is guaranteed to be small, this cannot really cause any issues even on 32-bit archs but let's be careful. Fixes: 9c2fc0de1a6e638fe58c354a463f544f42a90a09 Signed-off-by: Jan Kara Signed-off-by: Greg Kroah-Hartman --- fs/udf/file.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) --- a/fs/udf/file.c +++ b/fs/udf/file.c @@ -43,10 +43,15 @@ static void __udf_adinicb_readpage(struc struct inode *inode = page->mapping->host; char *kaddr; struct udf_inode_info *iinfo = UDF_I(inode); + loff_t isize = i_size_read(inode); + /* + * We have to be careful here as truncate can change i_size under us. + * So just sample it once and use the same value everywhere. + */ kaddr = kmap_atomic(page); - memcpy(kaddr, iinfo->i_ext.i_data + iinfo->i_lenEAttr, inode->i_size); - memset(kaddr + inode->i_size, 0, PAGE_SIZE - inode->i_size); + memcpy(kaddr, iinfo->i_ext.i_data + iinfo->i_lenEAttr, isize); + memset(kaddr + isize, 0, PAGE_SIZE - isize); flush_dcache_page(page); SetPageUptodate(page); kunmap_atomic(kaddr);