From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752025AbcEQDck (ORCPT ); Mon, 16 May 2016 23:32:40 -0400 Received: from p3plsmtps2ded02.prod.phx3.secureserver.net ([208.109.80.59]:56064 "EHLO p3plsmtps2ded02.prod.phx3.secureserver.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751103AbcEQDci (ORCPT ); Mon, 16 May 2016 23:32:38 -0400 x-originating-ip: 72.167.245.219 From: Dexuan Cui To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, driverdev-devel@linuxdriverproject.org, olaf@aepfle.de, apw@canonical.com, jasowang@redhat.com, kys@microsoft.com, vkuznets@redhat.com Cc: haiyangz@microsoft.com Subject: [PATCH] Drivers: hv: vmbus: fix the race when querying & updating the percpu list Date: Mon, 16 May 2016 22:13:00 -0700 Message-Id: <1463461980-13401-1-git-send-email-decui@microsoft.com> X-Mailer: git-send-email 1.7.4.1 X-CMAE-Envelope: MS4wfGn7TmsgfdHVMFrMJBmI1+/rJnJXYTNRWeCT95luln9OrTIBV2eGlnxuWfiEnU3ymwraxt0ATNF/MUuwUqYNKR1o6T2NuBC2BsObFKInvCjkE2fMg1W1 uj4PhnwqZMPge+lhA4Zd1okgC3rex0qSKuICksyZmRuRcFozakYiHZxD+o+QSb4qbiQzeI9RMsHib6mMmZKeP/SXdPmnECjKfvSMP99EHa8A25xewqnwSrYY Yn+wRC1M4LnNxwvW4abqSQb+oyK1eDBrL125/FgZpDFsRf33+rs/g20umApSMfdWDOrY5zifuVVapM704NVZIMIecveFM17Th4Wuiwlc5Vi8qOoZbyOQ/7eJ /Jf1VPZll6EDNVWLqxYZoLFTSlsbKfk6VZ+0KMS46r/EUdTgNrvdVDOhrTMAwYH13ZRYPRgVPSeXn6a0QWLYxMofkublHb/uFhJt0aEOLbU8TC/p1MA= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a rare race when we remove an entry from the global list hv_context.percpu_list[cpu] in hv_process_channel_removal() -> percpu_channel_deq() -> list_del(): at this time, if vmbus_on_event() -> process_chn_event() -> pcpu_relid2channel() is trying to query the list, we can get the general protection fault: general protection fault: 0000 [#1] SMP ... RIP: 0010:[] [] vmbus_on_event+0xc4/0x149 Similarly, we also have the issue in the code path: vmbus_process_offer() -> percpu_channel_enq(). We can resolve the issue by disabling the tasklet when updating the list. Reported-by: Rolf Neugebauer Signed-off-by: Dexuan Cui --- drivers/hv/channel.c | 3 +++ drivers/hv/channel_mgmt.c | 20 +++++++++----------- include/linux/hyperv.h | 3 +++ 3 files changed, 15 insertions(+), 11 deletions(-) diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 56dd261..7811cf9 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -546,8 +546,11 @@ static int vmbus_close_internal(struct vmbus_channel *channel) put_cpu(); smp_call_function_single(channel->target_cpu, reset_channel_cb, channel, true); + smp_call_function_single(channel->target_cpu, + percpu_channel_deq, channel, true); } else { reset_channel_cb(channel); + percpu_channel_deq(channel); put_cpu(); } diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index 38b682ba..c4b5c07 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -21,6 +21,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include +#include #include #include #include @@ -277,7 +278,7 @@ static void free_channel(struct vmbus_channel *channel) kfree(channel); } -static void percpu_channel_enq(void *arg) +void percpu_channel_enq(void *arg) { struct vmbus_channel *channel = arg; int cpu = smp_processor_id(); @@ -285,7 +286,7 @@ static void percpu_channel_enq(void *arg) list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]); } -static void percpu_channel_deq(void *arg) +void percpu_channel_deq(void *arg) { struct vmbus_channel *channel = arg; @@ -313,15 +314,6 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid) BUG_ON(!channel->rescind); BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex)); - if (channel->target_cpu != get_cpu()) { - put_cpu(); - smp_call_function_single(channel->target_cpu, - percpu_channel_deq, channel, true); - } else { - percpu_channel_deq(channel); - put_cpu(); - } - if (channel->primary_channel == NULL) { list_del(&channel->listentry); @@ -363,6 +355,7 @@ void vmbus_free_channels(void) */ static void vmbus_process_offer(struct vmbus_channel *newchannel) { + struct tasklet_struct *tasklet; struct vmbus_channel *channel; bool fnew = true; unsigned long flags; @@ -409,6 +402,8 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) init_vp_index(newchannel, dev_type); + tasklet = hv_context.event_dpc[newchannel->target_cpu]; + tasklet_disable(tasklet); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, @@ -418,6 +413,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) percpu_channel_enq(newchannel); put_cpu(); } + tasklet_enable(tasklet); /* * This state is used to indicate a successful open @@ -469,6 +465,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) list_del(&newchannel->listentry); mutex_unlock(&vmbus_connection.channel_mutex); + tasklet_disable(tasklet); if (newchannel->target_cpu != get_cpu()) { put_cpu(); smp_call_function_single(newchannel->target_cpu, @@ -477,6 +474,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) percpu_channel_deq(newchannel); put_cpu(); } + tasklet_enable(tasklet); err_free_chan: free_channel(newchannel); diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 7be7237..95aea09 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1328,6 +1328,9 @@ extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *, struct icmsg_negotiate *, u8 *, int, int); +void percpu_channel_enq(void *arg); +void percpu_channel_deq(void *arg); + void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid); /*