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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 863A1ECDFB8 for ; Tue, 24 Jul 2018 02:10:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4346220881 for ; Tue, 24 Jul 2018 02:10:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4346220881 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388335AbeGXDON (ORCPT ); Mon, 23 Jul 2018 23:14:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:54352 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388248AbeGXDON (ORCPT ); Mon, 23 Jul 2018 23:14:13 -0400 Received: from vmware.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (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 93D4920685; Tue, 24 Jul 2018 02:10:08 +0000 (UTC) Date: Mon, 23 Jul 2018 22:10:06 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: Ingo Molnar , Shuah Khan , Tom Zanussi , Hiraku Toyooka , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/3] [BUGFIX] tracing: Fix double free of event_trigger_data Message-ID: <20180723221006.60cc7aa9@vmware.local.home> In-Reply-To: <153149926702.11274.12489440326560729788.stgit@devbox> References: <153149923649.11274.14970833360963898112.stgit@devbox> <153149926702.11274.12489440326560729788.stgit@devbox> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 14 Jul 2018 01:27:47 +0900 Masami Hiramatsu wrote: > Fix a double free bug of event_trigger_data caused by > calling unregister_trigger() from register_snapshot_trigger(). > This kicks a kernel BUG if double free checker is enabled > as below; > > kernel BUG at /home/mhiramat/ksrc/linux/mm/slub.c:296! > invalid opcode: 0000 [#1] SMP PTI > CPU: 2 PID: 4312 Comm: ftracetest Not tainted 4.18.0-rc1+ #44 > Hardware name: ASUS All Series/B85M-G, BIOS 2108 08/11/2014 > RIP: 0010:set_freepointer.part.37+0x0/0x10 > Code: 41 b8 01 00 00 00 29 c8 4d 8d 0c 0c b9 10 00 00 00 50 e8 e3 28 23 00 8b 53 08 5e 5f 89 d1 81 e1 00 04 00 00 e9 e9 fe ff ff 90 <0f> 0b 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 48 c7 c6 90 7f 0d > RSP: 0018:ffffa799caa3bd90 EFLAGS: 00010246 > RAX: ffff9b825f8c8e80 RBX: ffff9b825f8c8e80 RCX: ffff9b825f8c8e80 > RDX: 0000000000021562 RSI: ffff9b830e9e70e0 RDI: 0000000000000202 > RBP: 0000000000000246 R08: 0000000000000001 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000000 R12: ffff9b830e0072c0 > R13: ffffeb8e0d7e3200 R14: ffffffff961db7af R15: 00000000fffffffe > FS: 00007f135ba9f700(0000) GS:ffff9b830e800000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000563736b5f3a2 CR3: 0000000295916005 CR4: 00000000001606e0 > Call Trace: > kfree+0x35d/0x380 > event_trigger_callback+0x13f/0x1c0 > event_trigger_write+0xf2/0x1a0 > ? lock_acquire+0x9f/0x200 > __vfs_write+0x26/0x170 > ? rcu_read_lock_sched_held+0x6b/0x80 > ? rcu_sync_lockdep_assert+0x2e/0x60 > ? __sb_start_write+0x13e/0x1a0 > ? vfs_write+0x18a/0x1b0 > vfs_write+0xc1/0x1b0 > ksys_write+0x45/0xa0 > do_syscall_64+0x60/0x200 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > unregister_trigger() will free given event_trigger_data > at last. But that event_trigger_data will be freed again > in event_trigger_callback() if register_snapshot_trigger() > is failed, and causes a double free bug. > > Registering the data should be the final operation in the > register function on normal path, because the trigger > must be ready for taking action right after it is > registered. Nice catch. I can reproduce this. But this patch is fixing the symptom and not the disease. > > Fixes: commit 93e31ffbf417 ("tracing: Add 'snapshot' event trigger command") > Signed-off-by: Masami Hiramatsu > Cc: Steven Rostedt > Cc: Ingo Molnar > Cc: Tom Zanussi > Cc: stable@vger.kernel.org > --- > kernel/trace/trace.c | 5 +++++ > kernel/trace/trace.h | 2 ++ > kernel/trace/trace_events_trigger.c | 10 ++++++---- > 3 files changed, 13 insertions(+), 4 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index f054bd6a1c66..2556d8c097d2 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -980,6 +980,11 @@ static void free_snapshot(struct trace_array *tr) > tr->allocated_snapshot = false; > } > > +void tracing_free_snapshot_instance(struct trace_array *tr) > +{ > + free_snapshot(tr); > +} > + > /** > * tracing_alloc_snapshot - allocate snapshot buffer. > * > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > index f8f86231ad90..03468bb8a79a 100644 > --- a/kernel/trace/trace.h > +++ b/kernel/trace/trace.h > @@ -1823,12 +1823,14 @@ static inline void trace_event_eval_update(struct trace_eval_map **map, int len) > #ifdef CONFIG_TRACER_SNAPSHOT > void tracing_snapshot_instance(struct trace_array *tr); > int tracing_alloc_snapshot_instance(struct trace_array *tr); > +void tracing_free_snapshot_instance(struct trace_array *tr); > #else > static inline void tracing_snapshot_instance(struct trace_array *tr) { } > static inline int tracing_alloc_snapshot_instance(struct trace_array *tr) > { > return 0; > } > +static inline void tracing_free_snapshot_instance(struct trace_array *tr) { } > #endif > > extern struct trace_iterator *tracepoint_print_iter; > diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c > index d18249683682..40e2f4406b2c 100644 > --- a/kernel/trace/trace_events_trigger.c > +++ b/kernel/trace/trace_events_trigger.c > @@ -1079,11 +1079,13 @@ register_snapshot_trigger(char *glob, struct event_trigger_ops *ops, > struct event_trigger_data *data, > struct trace_event_file *file) > { > - int ret = register_trigger(glob, ops, data, file); > + int free_if_fail = !file->tr->allocated_snapshot; > + int ret = 0; > > - if (ret > 0 && tracing_alloc_snapshot_instance(file->tr) != 0) { > - unregister_trigger(glob, ops, data, file); > - ret = 0; > + if (!tracing_alloc_snapshot_instance(file->tr)) { > + ret = register_trigger(glob, ops, data, file); > + if (ret == 0 && free_if_fail) > + tracing_free_snapshot_instance(file->tr); > } > > return ret; Really, when we register_trigger() we should be able to freely call unresgister_trigger() with no side effects like the above happens. Instead of doing the above, I believe this is a better approach: Thoughts? P.S. This brings up another minor bug. The failure should return ENOMEM not ENOENT. -- Steve diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index d18249683682..d15a746bcdfb 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -679,6 +679,7 @@ event_trigger_callback(struct event_command *cmd_ops, goto out_free; out_reg: + event_trigger_init(trigger_ops, trigger_data); ret = cmd_ops->reg(glob, trigger_ops, trigger_data, file); /* * The above returns on success the # of functions enabled, @@ -687,9 +688,9 @@ event_trigger_callback(struct event_command *cmd_ops, */ if (!ret) { ret = -ENOENT; - goto out_free; + goto out_free_trigger; } else if (ret < 0) - goto out_free; + goto out_free_trigger; ret = 0; out: return ret; @@ -699,6 +700,10 @@ event_trigger_callback(struct event_command *cmd_ops, cmd_ops->set_filter(NULL, trigger_data, NULL); kfree(trigger_data); goto out; + + out_free_trigger: + event_trigger_free(trigger_ops, trigger_data); + goto out; } /**