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authorDexuan Cui <decui@microsoft.com>2016-06-10 04:47:24 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-08-31 14:05:41 +0300
commit638fea33aee858cc665297a76f0039e95a28ce0c (patch)
treeb7d64f0d5feea234364b488021b729c1ef3434c0 /drivers/hv
parente0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c (diff)
downloadlinux-638fea33aee858cc665297a76f0039e95a28ce0c.tar.xz
Drivers: hv: vmbus: fix the race when querying & updating the percpu list
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 kernel fault. 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. The patch also moves vmbus_release_relid() to a later place where the channel has been removed from the per-cpu and the global lists. Reported-by: Rolf Neugebauer <rolf.neugebauer@docker.com> Signed-off-by: Dexuan Cui <decui@microsoft.com> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hv')
-rw-r--r--drivers/hv/channel.c6
-rw-r--r--drivers/hv/channel_mgmt.c32
2 files changed, 30 insertions, 8 deletions
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 9a88c63f6e0d..e47d37d21d56 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -505,7 +505,6 @@ static void reset_channel_cb(void *arg)
static int vmbus_close_internal(struct vmbus_channel *channel)
{
struct vmbus_channel_close_channel *msg;
- struct tasklet_struct *tasklet;
int ret;
/*
@@ -517,8 +516,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
* To resolve the race, we can serialize them by disabling the
* tasklet when the latter is running here.
*/
- tasklet = hv_context.event_dpc[channel->target_cpu];
- tasklet_disable(tasklet);
+ hv_event_tasklet_disable(channel);
/*
* In case a device driver's probe() fails (e.g.,
@@ -584,7 +582,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
get_order(channel->ringbuffer_pagecount * PAGE_SIZE));
out:
- tasklet_enable(tasklet);
+ hv_event_tasklet_enable(channel);
return ret;
}
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index b6c1211b4df7..8818b92e5912 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>
@@ -303,16 +304,32 @@ static void vmbus_release_relid(u32 relid)
vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released));
}
+void hv_event_tasklet_disable(struct vmbus_channel *channel)
+{
+ struct tasklet_struct *tasklet;
+ tasklet = hv_context.event_dpc[channel->target_cpu];
+ tasklet_disable(tasklet);
+}
+
+void hv_event_tasklet_enable(struct vmbus_channel *channel)
+{
+ struct tasklet_struct *tasklet;
+ tasklet = hv_context.event_dpc[channel->target_cpu];
+ tasklet_enable(tasklet);
+
+ /* In case there is any pending event */
+ tasklet_schedule(tasklet);
+}
+
void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
{
unsigned long flags;
struct vmbus_channel *primary_channel;
- vmbus_release_relid(relid);
-
BUG_ON(!channel->rescind);
BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));
+ hv_event_tasklet_disable(channel);
if (channel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(channel->target_cpu,
@@ -321,6 +338,7 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
percpu_channel_deq(channel);
put_cpu();
}
+ hv_event_tasklet_enable(channel);
if (channel->primary_channel == NULL) {
list_del(&channel->listentry);
@@ -341,6 +359,8 @@ void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid)
cpumask_clear_cpu(channel->target_cpu,
&primary_channel->alloced_cpus_in_node);
+ vmbus_release_relid(relid);
+
free_channel(channel);
}
@@ -409,6 +429,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
init_vp_index(newchannel, dev_type);
+ hv_event_tasklet_disable(newchannel);
if (newchannel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(newchannel->target_cpu,
@@ -418,6 +439,7 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
percpu_channel_enq(newchannel);
put_cpu();
}
+ hv_event_tasklet_enable(newchannel);
/*
* This state is used to indicate a successful open
@@ -463,12 +485,11 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
return;
err_deq_chan:
- vmbus_release_relid(newchannel->offermsg.child_relid);
-
mutex_lock(&vmbus_connection.channel_mutex);
list_del(&newchannel->listentry);
mutex_unlock(&vmbus_connection.channel_mutex);
+ hv_event_tasklet_disable(newchannel);
if (newchannel->target_cpu != get_cpu()) {
put_cpu();
smp_call_function_single(newchannel->target_cpu,
@@ -477,6 +498,9 @@ err_deq_chan:
percpu_channel_deq(newchannel);
put_cpu();
}
+ hv_event_tasklet_enable(newchannel);
+
+ vmbus_release_relid(newchannel->offermsg.child_relid);
err_free_chan:
free_channel(newchannel);