Drivers: hv: utils: introduce HVUTIL_TRANSPORT_DESTROY mode
When Hyper-V host asks us to remove some util driver by closing the
appropriate channel there is no easy way to force the current file
descriptor holder to hang up but we can start to respond -EBADF to all
operations asking it to exit gracefully.
As we're setting hvt->mode from two separate contexts now we need to use
a proper locking.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/hv/hv_utils_transport.c b/drivers/hv/hv_utils_transport.c
index 59c6f3d..31c2f86 100644
--- a/drivers/hv/hv_utils_transport.c
+++ b/drivers/hv/hv_utils_transport.c
@@ -27,11 +27,9 @@
static void hvt_reset(struct hvutil_transport *hvt)
{
- mutex_lock(&hvt->lock);
kfree(hvt->outmsg);
hvt->outmsg = NULL;
hvt->outmsg_len = 0;
- mutex_unlock(&hvt->lock);
if (hvt->on_reset)
hvt->on_reset();
}
@@ -44,10 +42,17 @@
hvt = container_of(file->f_op, struct hvutil_transport, fops);
- if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0))
+ if (wait_event_interruptible(hvt->outmsg_q, hvt->outmsg_len > 0 ||
+ hvt->mode != HVUTIL_TRANSPORT_CHARDEV))
return -EINTR;
mutex_lock(&hvt->lock);
+
+ if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
+ ret = -EBADF;
+ goto out_unlock;
+ }
+
if (!hvt->outmsg) {
ret = -EAGAIN;
goto out_unlock;
@@ -85,7 +90,10 @@
if (IS_ERR(inmsg))
return PTR_ERR(inmsg);
- ret = hvt->on_msg(inmsg, count);
+ if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
+ ret = -EBADF;
+ else
+ ret = hvt->on_msg(inmsg, count);
kfree(inmsg);
@@ -99,6 +107,10 @@
hvt = container_of(file->f_op, struct hvutil_transport, fops);
poll_wait(file, &hvt->outmsg_q, wait);
+
+ if (hvt->mode == HVUTIL_TRANSPORT_DESTROY)
+ return -EBADF;
+
if (hvt->outmsg_len > 0)
return POLLIN | POLLRDNORM;
@@ -108,26 +120,39 @@
static int hvt_op_open(struct inode *inode, struct file *file)
{
struct hvutil_transport *hvt;
+ int ret = 0;
+ bool issue_reset = false;
hvt = container_of(file->f_op, struct hvutil_transport, fops);
- /*
- * Switching to CHARDEV mode. We switch bach to INIT when device
- * gets released.
- */
- if (hvt->mode == HVUTIL_TRANSPORT_INIT)
+ mutex_lock(&hvt->lock);
+
+ if (hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
+ ret = -EBADF;
+ } else if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
+ /*
+ * Switching to CHARDEV mode. We switch bach to INIT when
+ * device gets released.
+ */
hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
+ }
else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
/*
* We're switching from netlink communication to using char
* device. Issue the reset first.
*/
- hvt_reset(hvt);
+ issue_reset = true;
hvt->mode = HVUTIL_TRANSPORT_CHARDEV;
- } else
- return -EBUSY;
+ } else {
+ ret = -EBUSY;
+ }
- return 0;
+ if (issue_reset)
+ hvt_reset(hvt);
+
+ mutex_unlock(&hvt->lock);
+
+ return ret;
}
static int hvt_op_release(struct inode *inode, struct file *file)
@@ -136,12 +161,15 @@
hvt = container_of(file->f_op, struct hvutil_transport, fops);
- hvt->mode = HVUTIL_TRANSPORT_INIT;
+ mutex_lock(&hvt->lock);
+ if (hvt->mode != HVUTIL_TRANSPORT_DESTROY)
+ hvt->mode = HVUTIL_TRANSPORT_INIT;
/*
* Cleanup message buffers to avoid spurious messages when the daemon
* connects back.
*/
hvt_reset(hvt);
+ mutex_unlock(&hvt->lock);
return 0;
}
@@ -168,6 +196,7 @@
* Switching to NETLINK mode. Switching to CHARDEV happens when someone
* opens the device.
*/
+ mutex_lock(&hvt->lock);
if (hvt->mode == HVUTIL_TRANSPORT_INIT)
hvt->mode = HVUTIL_TRANSPORT_NETLINK;
@@ -175,6 +204,7 @@
hvt_found->on_msg(msg->data, msg->len);
else
pr_warn("hvt_cn_callback: unexpected netlink message!\n");
+ mutex_unlock(&hvt->lock);
}
int hvutil_transport_send(struct hvutil_transport *hvt, void *msg, int len)
@@ -182,7 +212,8 @@
struct cn_msg *cn_msg;
int ret = 0;
- if (hvt->mode == HVUTIL_TRANSPORT_INIT) {
+ if (hvt->mode == HVUTIL_TRANSPORT_INIT ||
+ hvt->mode == HVUTIL_TRANSPORT_DESTROY) {
return -EINVAL;
} else if (hvt->mode == HVUTIL_TRANSPORT_NETLINK) {
cn_msg = kzalloc(sizeof(*cn_msg) + len, GFP_ATOMIC);
@@ -198,6 +229,11 @@
}
/* HVUTIL_TRANSPORT_CHARDEV */
mutex_lock(&hvt->lock);
+ if (hvt->mode != HVUTIL_TRANSPORT_CHARDEV) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
if (hvt->outmsg) {
/* Previous message wasn't received */
ret = -EFAULT;
@@ -268,6 +304,11 @@
void hvutil_transport_destroy(struct hvutil_transport *hvt)
{
+ mutex_lock(&hvt->lock);
+ hvt->mode = HVUTIL_TRANSPORT_DESTROY;
+ wake_up_interruptible(&hvt->outmsg_q);
+ mutex_unlock(&hvt->lock);
+
spin_lock(&hvt_list_lock);
list_del(&hvt->list);
spin_unlock(&hvt_list_lock);
diff --git a/drivers/hv/hv_utils_transport.h b/drivers/hv/hv_utils_transport.h
index bff4c92..06254a1 100644
--- a/drivers/hv/hv_utils_transport.h
+++ b/drivers/hv/hv_utils_transport.h
@@ -25,6 +25,7 @@
HVUTIL_TRANSPORT_INIT = 0,
HVUTIL_TRANSPORT_NETLINK,
HVUTIL_TRANSPORT_CHARDEV,
+ HVUTIL_TRANSPORT_DESTROY,
};
struct hvutil_transport {