Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753152AbdFPNLX (ORCPT ); Fri, 16 Jun 2017 09:11:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34924 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752647AbdFPNLW (ORCPT ); Fri, 16 Jun 2017 09:11:22 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 998C264D86 Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=tcamuso@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 998C264D86 Subject: Re: [PATCH] ipmi: use rcu lock around call to intf->handlers->sender() To: minyard@acm.org, openipmi-developer@lists.sourceforge.net References: <1497365651-7413-1-git-send-email-tcamuso@redhat.com> <1a359a04-f1da-0e2e-8663-6527e84dd5a3@acm.org> <613dc158-e3de-f713-019e-cf8c190e72be@acm.org> Cc: linux-kernel@vger.kernel.org From: Tony Camuso Message-ID: Date: Fri, 16 Jun 2017 09:11:20 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <613dc158-e3de-f713-019e-cf8c190e72be@acm.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 16 Jun 2017 13:11:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7293 Lines: 163 On 06/16/2017 08:15 AM, Corey Minyard wrote: > On 06/15/2017 10:54 AM, Corey Minyard wrote: >> On 06/13/2017 09:54 AM, Tony Camuso wrote: >>> A vendor with a system having more than 128 CPUs occasionally encounters a >>> crash during shutdown. This is not an easily reproduceable event, but the >>> vendor was able to provide the following analysis of the crash, which >>> exhibits the same footprint each time. >>> >>> crash> bt >>> PID: 0 TASK: ffff88017c70ce70 CPU: 5 COMMAND: "swapper/5" >>> #0 [ffff88085c143ac8] machine_kexec at ffffffff81059c8b >>> #1 [ffff88085c143b28] __crash_kexec at ffffffff811052e2 >>> #2 [ffff88085c143bf8] crash_kexec at ffffffff811053d0 >>> #3 [ffff88085c143c10] oops_end at ffffffff8168ef88 >>> #4 [ffff88085c143c38] no_context at ffffffff8167ebb3 >>> #5 [ffff88085c143c88] __bad_area_nosemaphore at ffffffff8167ec49 >>> #6 [ffff88085c143cd0] bad_area_nosemaphore at ffffffff8167edb3 >>> #7 [ffff88085c143ce0] __do_page_fault at ffffffff81691d1e >>> #8 [ffff88085c143d40] do_page_fault at ffffffff81691ec5 >>> #9 [ffff88085c143d70] page_fault at ffffffff8168e188 >>> [exception RIP: unknown or invalid address] >>> RIP: ffffffffa053c800 RSP: ffff88085c143e28 RFLAGS: 00010206 >>> RAX: ffff88017c72bfd8 RBX: ffff88017a8dc000 RCX: ffff8810588b5ac8 >>> RDX: ffff8810588b5a00 RSI: ffffffffa053c800 RDI: ffff8810588b5a00 >>> RBP: ffff88085c143e58 R8: ffff88017c70d408 R9: ffff88017a8dc000 >>> R10: 0000000000000002 R11: ffff88085c143da0 R12: ffff8810588b5ac8 >>> R13: 0000000000000100 R14: ffffffffa053c800 R15: ffff8810588b5a00 >>> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 >>> --- --- >>> [exception RIP: cpuidle_enter_state+82] >>> RIP: ffffffff81514192 RSP: ffff88017c72be50 RFLAGS: 00000202 >>> RAX: 0000001e4c3c6f16 RBX: 000000000000f8a0 RCX: 0000000000000018 >>> RDX: 0000000225c17d03 RSI: ffff88017c72bfd8 RDI: 0000001e4c3c6f16 >>> RBP: ffff88017c72be78 R8: 000000000000237e R9: 0000000000000018 >>> R10: 0000000000002494 R11: 0000000000000001 R12: ffff88017c72be20 >>> R13: ffff88085c14f8e0 R14: 0000000000000082 R15: 0000001e4c3bb400 >>> ORIG_RAX: ffffffffffffff10 CS: 0010 SS: 0018 >>> >>> This is the corresponding stack trace >>> >>> It has crashed because the area pointed with RIP extracted from timer >>> element is already removed during a shutdown process. >>> >>> The function is smi_timeout(). >>> >>> And we think ffff8810588b5a00 in RDX is a parameter struct smi_info >>> >>> crash> rd ffff8810588b5a00 20 >>> ffff8810588b5a00: ffff8810588b6000 0000000000000000 .`.X............ >>> ffff8810588b5a10: ffff880853264400 ffffffffa05417e0 .D&S......T..... >>> ffff8810588b5a20: 24a024a000000000 0000000000000000 .....$.$........ >>> ffff8810588b5a30: 0000000000000000 0000000000000000 ................ >>> ffff8810588b5a40: ffffffffa053a040 ffffffffa053a060 @.S.....`.S..... >>> ffff8810588b5a50: 0000000000000000 0000000100000001 ................ >>> ffff8810588b5a60: 0000000000000000 0000000000000e00 ................ >>> ffff8810588b5a70: ffffffffa053a580 ffffffffa053a6e0 ..S.......S..... >>> ffff8810588b5a80: ffffffffa053a4a0 ffffffffa053a250 ..S.....P.S..... >>> ffff8810588b5a90: 0000000500000002 0000000000000000 ................ >>> >>> Unfortunately the top of this area is already detroyed by someone. >>> But because of two reasonns we think this is struct smi_info >>> 1) The address included in between ffff8810588b5a70 and ffff8810588b5a80: >>> are inside of ipmi_si_intf.c see crash> module ffff88085779d2c0 >>> >>> 2) We've found the area which point this. >>> It is offset 0x68 of ffff880859df4000 >>> >>> crash> rd ffff880859df4000 100 >>> ffff880859df4000: 0000000000000000 0000000000000001 ................ >>> ffff880859df4010: ffffffffa0535290 dead000000000200 .RS............. >>> ffff880859df4020: ffff880859df4020 ffff880859df4020 @.Y.... @.Y.... >>> ffff880859df4030: 0000000000000002 0000000000100010 ................ >>> ffff880859df4040: ffff880859df4040 ffff880859df4040 @@.Y....@@.Y.... >>> ffff880859df4050: 0000000000000000 0000000000000000 ................ >>> ffff880859df4060: 0000000000000000 ffff8810588b5a00 .........Z.X.... >>> ffff880859df4070: 0000000000000001 ffff880859df4078 ........x@.Y.... >>> >>> If we regards it as struct ipmi_smi in shutdown process >>> it looks consistent. >>> >>> The remedy for this apparent race is affixed below. >> >> I think you are right about this problem, but in_shutdown is checked already >> a bit before when newmsg is extracted from the list. Wouldn't it be better >> to add the rcu_read_lock() region starting right before the previous >> in_shutdown check to after the send? That would avoid a leak in this >> case. > > While lying awake unable to sleep, I realized that you can't call the > sender function while holding rcu_read_lock(). That will break RT, > because you can't claim a mutex while holding rcu_read_lock(), > and the sender function will claim normal spinlocks. > > So I need to think about this a bit. > > -corey > >> >> Thanks, >> >> -corey >> Would this be adequate to prevent the race? Is the sender's mutex/spinlock sufficient to limit access? diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index 9f69995..ebce6b3 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -3880,6 +3880,7 @@ static void smi_recv_tasklet(unsigned long val) */ if (!run_to_completion) spin_lock_irqsave(&intf->xmit_msgs_lock, flags); + if (intf->curr_msg == NULL && !intf->in_shutdown) { struct list_head *entry = NULL; @@ -3894,11 +3895,13 @@ static void smi_recv_tasklet(unsigned long val) newmsg = list_entry(entry, struct ipmi_smi_msg, link); intf->curr_msg = newmsg; } + + if (newmsg) + intf->handlers->sender(intf->send_info, newmsg); } + if (!run_to_completion) spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags); - if (newmsg) - intf->handlers->sender(intf->send_info, newmsg); handle_new_recv_msgs(intf); } >>> Signed-off-by: Tony Camuso >>> --- >>> drivers/char/ipmi/ipmi_msghandler.c | 9 +++++++-- >>> 1 file changed, 7 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c >>> index 9f69995..577509f 100644 >>> --- a/drivers/char/ipmi/ipmi_msghandler.c >>> +++ b/drivers/char/ipmi/ipmi_msghandler.c >>> @@ -3897,8 +3897,13 @@ static void smi_recv_tasklet(unsigned long val) >>> } >>> if (!run_to_completion) >>> spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags); >>> - if (newmsg) >>> - intf->handlers->sender(intf->send_info, newmsg); >>> + >>> + if (newmsg) { >>> + rcu_read_lock(); >>> + if (!intf->in_shutdown) >>> + intf->handlers->sender(intf->send_info, newmsg); >>> + rcu_read_unlock(); >>> + } >>> handle_new_recv_msgs(intf); >>> } >> >> >