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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 6768BC10F00 for ; Tue, 2 Apr 2019 13:45:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40FB720856 for ; Tue, 2 Apr 2019 13:45:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731297AbfDBNpJ (ORCPT ); Tue, 2 Apr 2019 09:45:09 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43396 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731466AbfDBNkI (ORCPT ); Tue, 2 Apr 2019 09:40:08 -0400 Received: from [167.98.27.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hBJe0-0002oc-J3; Tue, 02 Apr 2019 14:40:04 +0100 Received: from ben by deadeye with local (Exim 4.92) (envelope-from ) id 1hBJdx-0004wz-NJ; Tue, 02 Apr 2019 14:40:01 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Theodore Ts'o" Date: Tue, 02 Apr 2019 14:38:28 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 81/99] ext4: fix a potential fiemap/page fault deadlock w/ inline_data In-Reply-To: X-SA-Exim-Connect-IP: 167.98.27.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.65-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o commit 2b08b1f12cd664dc7d5c84ead9ff25ae97ad5491 upstream. The ext4_inline_data_fiemap() function calls fiemap_fill_next_extent() while still holding the xattr semaphore. This is not necessary and it triggers a circular lockdep warning. This is because fiemap_fill_next_extent() could trigger a page fault when it writes into page which triggers a page fault. If that page is mmaped from the inline file in question, this could very well result in a deadlock. This problem can be reproduced using generic/519 with a file system configuration which has the inline_data feature enabled. Signed-off-by: Theodore Ts'o Signed-off-by: Ben Hutchings --- fs/ext4/inline.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/fs/ext4/inline.c +++ b/fs/ext4/inline.c @@ -1846,12 +1846,12 @@ int ext4_inline_data_fiemap(struct inode physical += (char *)ext4_raw_inode(&iloc) - iloc.bh->b_data; physical += offsetof(struct ext4_inode, i_block); - if (physical) - error = fiemap_fill_next_extent(fieinfo, start, physical, - inline_len, flags); brelse(iloc.bh); out: up_read(&EXT4_I(inode)->xattr_sem); + if (physical) + error = fiemap_fill_next_extent(fieinfo, start, physical, + inline_len, flags); return (error < 0 ? error : 0); }