From patchwork Fri Jan 6 14:11:34 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Sterba X-Patchwork-Id: 9501079 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id B700E6021C for ; Fri, 6 Jan 2017 14:14:01 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C49A8284CF for ; Fri, 6 Jan 2017 14:14:01 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B99CD284CC; Fri, 6 Jan 2017 14:14:01 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham 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 23318284C9 for ; Fri, 6 Jan 2017 14:14:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755524AbdAFONP (ORCPT ); Fri, 6 Jan 2017 09:13:15 -0500 Received: from mx2.suse.de ([195.135.220.15]:50772 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933530AbdAFOND (ORCPT ); Fri, 6 Jan 2017 09:13:03 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id E188BAAC4; Fri, 6 Jan 2017 14:11:50 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 92484DA7AF; Fri, 6 Jan 2017 15:11:35 +0100 (CET) From: David Sterba To: linux-btrfs@vger.kernel.org Cc: bigeasy@linutronix.de, quwenruo@cn.fujitsu.com, David Sterba , stable@vger.kernel.org, #@suse.cz, 4.8+@suse.cz Subject: [PATCH] btrfs: fix crash when tracepoint arguments are freed by wq callbacks Date: Fri, 6 Jan 2017 15:11:34 +0100 Message-Id: <20170106141134.8133-1-dsterba@suse.com> X-Mailer: git-send-email 2.10.1 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Enabling btrfs tracepoints leads to instant crash, as reported. The wq callbacks could free the memory and the tracepoints started to dereference the members to get to fs_info. The proposed fix https://marc.info/?l=linux-btrfs&m=148172436722606&w=2 removed the tracepoints but we could preserve them by passing only the required data in a safe way. Fixes: bc074524e123 ("btrfs: prefix fsid to all trace events") CC: stable@vger.kernel.org # 4.8+ Reported-by: Sebastian Andrzej Siewior Signed-off-by: David Sterba Reviewed-by: Qu Wenruo --- fs/btrfs/async-thread.c | 15 +++++++++++---- include/trace/events/btrfs.h | 22 +++++++++++++--------- 2 files changed, 24 insertions(+), 13 deletions(-) diff --git a/fs/btrfs/async-thread.c b/fs/btrfs/async-thread.c index 63d197724519..ff0b0be92d61 100644 --- a/fs/btrfs/async-thread.c +++ b/fs/btrfs/async-thread.c @@ -273,6 +273,8 @@ static void run_ordered_work(struct __btrfs_workqueue *wq) unsigned long flags; while (1) { + void *wtag; + spin_lock_irqsave(lock, flags); if (list_empty(list)) break; @@ -299,11 +301,13 @@ static void run_ordered_work(struct __btrfs_workqueue *wq) spin_unlock_irqrestore(lock, flags); /* - * we don't want to call the ordered free functions - * with the lock held though + * We don't want to call the ordered free functions with the + * lock held though. Save the work as tag for the trace event, + * because the callback could free the structure. */ + wtag = work; work->ordered_free(work); - trace_btrfs_all_work_done(work); + trace_btrfs_all_work_done(wq->fs_info, wtag); } spin_unlock_irqrestore(lock, flags); } @@ -311,6 +315,7 @@ static void run_ordered_work(struct __btrfs_workqueue *wq) static void normal_work_helper(struct btrfs_work *work) { struct __btrfs_workqueue *wq; + void *wtag; int need_order = 0; /* @@ -324,6 +329,8 @@ static void normal_work_helper(struct btrfs_work *work) if (work->ordered_func) need_order = 1; wq = work->wq; + /* Safe for tracepoints in case work gets freed by the callback */ + wtag = work; trace_btrfs_work_sched(work); thresh_exec_hook(wq); @@ -333,7 +340,7 @@ static void normal_work_helper(struct btrfs_work *work) run_ordered_work(wq); } if (!need_order) - trace_btrfs_all_work_done(work); + trace_btrfs_all_work_done(wq->fs_info, wtag); } void btrfs_init_work(struct btrfs_work *work, btrfs_work_func_t uniq_func, diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h index c14bed4ab097..b09225c77676 100644 --- a/include/trace/events/btrfs.h +++ b/include/trace/events/btrfs.h @@ -1157,22 +1157,26 @@ DECLARE_EVENT_CLASS(btrfs__work, __entry->func, __entry->ordered_func, __entry->ordered_free) ); -/* For situiations that the work is freed */ +/* + * For situiations when the work is freed, we pass fs_info and a tag that that + * matches address of the work structure so it can be paired with the + * scheduling event. + */ DECLARE_EVENT_CLASS(btrfs__work__done, - TP_PROTO(struct btrfs_work *work), + TP_PROTO(struct btrfs_fs_info *fs_info, void *wtag), - TP_ARGS(work), + TP_ARGS(fs_info, wtag), TP_STRUCT__entry_btrfs( - __field( void *, work ) + __field( void *, wtag ) ), - TP_fast_assign_btrfs(btrfs_work_owner(work), - __entry->work = work; + TP_fast_assign_btrfs(fs_info, + __entry->wtag = wtag; ), - TP_printk_btrfs("work->%p", __entry->work) + TP_printk_btrfs("work->%p", __entry->wtag) ); DEFINE_EVENT(btrfs__work, btrfs_work_queued, @@ -1191,9 +1195,9 @@ DEFINE_EVENT(btrfs__work, btrfs_work_sched, DEFINE_EVENT(btrfs__work__done, btrfs_all_work_done, - TP_PROTO(struct btrfs_work *work), + TP_PROTO(struct btrfs_fs_info *fs_info, void *wtag), - TP_ARGS(work) + TP_ARGS(fs_info, wtag) ); DEFINE_EVENT(btrfs__work, btrfs_ordered_sched,