From patchwork Wed Nov 28 19:44:07 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Williams X-Patchwork-Id: 10703295 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9801A14BD for ; Wed, 28 Nov 2018 19:56:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 884412D727 for ; Wed, 28 Nov 2018 19:56:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7BD932DD1D; Wed, 28 Nov 2018 19:56:38 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 264452D727 for ; Wed, 28 Nov 2018 19:56:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729196AbeK2G7X (ORCPT ); Thu, 29 Nov 2018 01:59:23 -0500 Received: from mga11.intel.com ([192.55.52.93]:41846 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725994AbeK2G7X (ORCPT ); Thu, 29 Nov 2018 01:59:23 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Nov 2018 11:56:35 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,291,1539673200"; d="scan'208";a="113219463" Received: from dwillia2-desk3.jf.intel.com (HELO dwillia2-desk3.amr.corp.intel.com) ([10.54.39.16]) by orsmga001.jf.intel.com with ESMTP; 28 Nov 2018 11:56:35 -0800 Subject: [PATCH v2] dax: Don't access a freed inode From: Dan Williams To: linux-fsdevel@vger.kernel.org Cc: stable@vger.kernel.org, Matthew Wilcox , Jan Kara , stable@vger.kernel.org, linux-nvdimm@lists.01.org Date: Wed, 28 Nov 2018 11:44:07 -0800 Message-ID: <154343424782.982643.12596428619928518745.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <20181127211634.4995-3-willy@infradead.org> References: <20181127211634.4995-3-willy@infradead.org> User-Agent: StGit/0.18-2-gc94f MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Wilcox After we drop the i_pages lock, the inode can be freed at any time. The get_unlocked_entry() code has no choice but to reacquire the lock, so it can't be used here. Create a new wait_entry_unlocked() which takes care not to acquire the lock or dereference the address_space in any way. Fixes: c2a7d2a11552 ("filesystem-dax: Introduce dax_lock_mapping_entry()") Cc: Signed-off-by: Matthew Wilcox Reviewed-by: Jan Kara Signed-off-by: Dan Williams --- fs/dax.c | 32 +++++++++++++++++++++++++++++--- 1 file changed, 29 insertions(+), 3 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index e69fc231833b..3f592dc18d67 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -232,6 +232,34 @@ static void *get_unlocked_entry(struct xa_state *xas) } } +/* + * The only thing keeping the address space around is the i_pages lock + * (it's cycled in clear_inode() after removing the entries from i_pages) + * After we call xas_unlock_irq(), we cannot touch xas->xa. + */ +static void wait_entry_unlocked(struct xa_state *xas, void *entry) +{ + struct wait_exceptional_entry_queue ewait; + wait_queue_head_t *wq; + + init_wait(&ewait.wait); + ewait.wait.func = wake_exceptional_entry_func; + + wq = dax_entry_waitqueue(xas, entry, &ewait.key); + prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); + xas_unlock_irq(xas); + schedule(); + finish_wait(wq, &ewait.wait); + + /* + * Entry lock waits are exclusive. Wake up the next waiter since + * we aren't sure we will acquire the entry lock and thus wake + * the next waiter up on unlock. + */ + if (waitqueue_active(wq)) + __wake_up(wq, TASK_NORMAL, 1, &ewait.key); +} + static void put_unlocked_entry(struct xa_state *xas, void *entry) { /* If we were the only waiter woken, wake the next one */ @@ -389,9 +417,7 @@ bool dax_lock_mapping_entry(struct page *page) entry = xas_load(&xas); if (dax_is_locked(entry)) { rcu_read_unlock(); - entry = get_unlocked_entry(&xas); - xas_unlock_irq(&xas); - put_unlocked_entry(&xas, entry); + wait_entry_unlocked(&xas, entry); rcu_read_lock(); continue; }