From: Dexuan Cui <decui@microsoft.com>
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 [thread overview]
Message-ID: <1463461980-13401-1-git-send-email-decui@microsoft.com> (raw)
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:[<ffffffff81461b6b>] [<ffffffff81461b6b>] 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 <rolf.neugebauer@docker.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
---
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 <linux/kernel.h>
+#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
@@ -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);
/*
next reply other threads:[~2016-05-17 3:32 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-17 5:13 Dexuan Cui [this message]
2016-05-17 8:14 ` [PATCH] Drivers: hv: vmbus: fix the race when querying & updating the percpu list Vitaly Kuznetsov
2016-05-17 8:35 ` Dexuan Cui
2016-05-17 8:37 ` Dexuan Cui
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1463461980-13401-1-git-send-email-decui@microsoft.com \
--to=decui@microsoft.com \
--cc=apw@canonical.com \
--cc=driverdev-devel@linuxdriverproject.org \
--cc=gregkh@linuxfoundation.org \
--cc=haiyangz@microsoft.com \
--cc=jasowang@redhat.com \
--cc=kys@microsoft.com \
--cc=linux-kernel@vger.kernel.org \
--cc=olaf@aepfle.de \
--cc=vkuznets@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).