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Drivers: hv: vmbus: fix the race when querying & updating the percpu list

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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>
This commit is contained in:
Dexuan Cui 2016-06-09 18:47:24 -07:00 committed by Greg Kroah-Hartman
parent e0fa3e5e7d
commit 638fea33ae
3 changed files with 33 additions and 8 deletions
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6
drivers/hv/channel.c
View File

@ -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;
}

32
drivers/hv/channel_mgmt.c
View File

@ -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);

3
include/linux/hyperv.h
View File

@ -1357,6 +1357,9 @@ extern bool vmbus_prep_negotiate_resp(struct icmsg_hdr *,
struct icmsg_negotiate *, u8 *, int,
int);
void hv_event_tasklet_disable(struct vmbus_channel *channel);
void hv_event_tasklet_enable(struct vmbus_channel *channel);
void hv_process_channel_removal(struct vmbus_channel *channel, u32 relid);
/*