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vmbus: use rcu for per-cpu channel list

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The per-cpu channel list is now referred to in the interrupt
routine. This is mostly safe since the host will not normally generate
an interrupt when channel is being deleted but if it did then there
would be a use after free problem.

To solve, this use RCU protection on ther per-cpu list.

Fixes: 631e63a9f3 ("vmbus: change to per channel tasklet")

Signed-off-by: Stephen Hemminger <sthemmin@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:
Stephen Hemminger 2017-03-04 18:13:57 -07:00 committed by Greg Kroah-Hartman
parent c6240cacdb
commit 8200f2085a
3 changed files with 16 additions and 4 deletions
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7
drivers/hv/channel_mgmt.c
View file

@ -350,7 +350,8 @@ static struct vmbus_channel *alloc_channel(void)
static void free_channel(struct vmbus_channel *channel)
{
tasklet_kill(&channel->callback_event);
kfree(channel);
kfree_rcu(channel, rcu);
}
static void percpu_channel_enq(void *arg)
@ -359,14 +360,14 @@ static void percpu_channel_enq(void *arg)
struct hv_per_cpu_context *hv_cpu
= this_cpu_ptr(hv_context.cpu_context);
list_add_tail(&channel->percpu_list, &hv_cpu->chan_list);
list_add_tail_rcu(&channel->percpu_list, &hv_cpu->chan_list);
}
static void percpu_channel_deq(void *arg)
{
struct vmbus_channel *channel = arg;
list_del(&channel->percpu_list);
list_del_rcu(&channel->percpu_list);
}

6
drivers/hv/vmbus_drv.c
View file

@ -939,8 +939,10 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
if (relid == 0)
continue;
rcu_read_lock();
/* Find channel based on relid */
list_for_each_entry(channel, &hv_cpu->chan_list, percpu_list) {
list_for_each_entry_rcu(channel, &hv_cpu->chan_list, percpu_list) {
if (channel->offermsg.child_relid != relid)
continue;
@ -956,6 +958,8 @@ static void vmbus_chan_sched(struct hv_per_cpu_context *hv_cpu)
tasklet_schedule(&channel->callback_event);
}
}
rcu_read_unlock();
}
}

7
include/linux/hyperv.h
View file

@ -845,6 +845,13 @@ struct vmbus_channel {
* link up channels based on their CPU affinity.
*/
struct list_head percpu_list;
/*
* Defer freeing channel until after all cpu's have
* gone through grace period.
*/
struct rcu_head rcu;
/*
* For performance critical channels (storage, networking
* etc,), Hyper-V has a mechanism to enhance the throughput