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Subject[PATCH] Drivers: hv: vmbus: Add mutex lock to channel show functions
The channel level "_show" functions are vulnerable to race conditions.
Add a mutex lock and unlock around the call to the channel level "_show"
functions in vmbus_chan_attr_show().

This problem was discussed here: https://lkml.org/lkml/2018/10/18/830

Signed-off-by: Kimberly Brown <kimbrownkd@gmail.com>
---
drivers/hv/vmbus_drv.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 403fee01572c..e8189bc168da 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1414,6 +1414,7 @@ static ssize_t vmbus_chan_attr_show(struct kobject *kobj,
= container_of(attr, struct vmbus_chan_attribute, attr);
const struct vmbus_channel *chan
= container_of(kobj, struct vmbus_channel, kobj);
+ ssize_t ret;

if (!attribute->show)
return -EIO;
@@ -1421,7 +1422,10 @@ static ssize_t vmbus_chan_attr_show(struct kobject *kobj,
if (chan->state != CHANNEL_OPENED_STATE)
return -EINVAL;

- return attribute->show(chan, buf);
+ mutex_lock(&vmbus_connection.channel_mutex);
+ ret = attribute->show(chan, buf);
+ mutex_unlock(&vmbus_connection.channel_mutex);
+ return ret;
}

static const struct sysfs_ops vmbus_chan_sysfs_ops = {
--
2.17.1
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