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Message-Id: <20210312022737.44122-1-skhan@linuxfoundation.org>
Date: Thu, 11 Mar 2021 19:27:37 -0700
From: Shuah Khan <skhan@...uxfoundation.org>
To: valentina.manea.m@...il.com, shuah@...nel.org,
gregkh@...uxfoundation.org
Cc: Shuah Khan <skhan@...uxfoundation.org>, linux-usb@...r.kernel.org,
linux-kernel@...r.kernel.org,
syzbot+a93fba6d384346a761e3@...kaller.appspotmail.com
Subject: [PATCH] usbip: fix vhci races in connection tear down
vhci_shutdown_connection() references connection state (tcp_socket,
tcp_rx, tcp_tx, sockfd) saved in usbpip_device without holding the
lock.
Current connection tear down sequence:
Step 1: shutdown the socket
Step 2: stop rx thread and reset tcp_rx pointer
Step 3: stop tx thread and reset tcp_tx pointer
Step 4: Reset tcp_socket and sockfd
There are several race windows between these steps. In addition, device
reset routine (vhci_device_reset) resets tcp_socket and sockfd holding
the lock.
Fix these races:
- Introduce in_disconnect flag to ensure vhci_shutdown_connection() runs
only once.
- Change attach_store() to initialize in_disconnect to false while
initializing connection status (tcp_socket, tcp_rx, tcp_tx, sockfd)
- Change vhci_shutdown_connection() to check in_disconnect and bail
out if disconnect is in progress.
- Change vhci_shutdown_connection() to
-- hold lock to save connection state pointers and unlock.
-- Shutdown the socket and stop threads.
-- Hold lock to clear connection status and in_disconnect flag.
- Change vhci_device_reset() to reset tcp_socket and sockfd.
if !in_disconnect
Tested syzbot and the reproducer did not trigger any issue.
Reported-and-tested-by: syzbot+a93fba6d384346a761e3@...kaller.appspotmail.com
Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
---
drivers/usb/usbip/usbip_common.h | 1 +
drivers/usb/usbip/vhci_hcd.c | 55 +++++++++++++++++++++++---------
drivers/usb/usbip/vhci_sysfs.c | 4 +++
3 files changed, 45 insertions(+), 15 deletions(-)
diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h
index d60ce17d3dd2..f6261c5a8c91 100644
--- a/drivers/usb/usbip/usbip_common.h
+++ b/drivers/usb/usbip/usbip_common.h
@@ -268,6 +268,7 @@ struct usbip_device {
struct task_struct *tcp_rx;
struct task_struct *tcp_tx;
+ bool in_disconnect; /* run device disconnect just once */
unsigned long event;
wait_queue_head_t eh_waitq;
diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 3209b5ddd30c..c1917efe5737 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -1007,31 +1007,54 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
static void vhci_shutdown_connection(struct usbip_device *ud)
{
struct vhci_device *vdev = container_of(ud, struct vhci_device, ud);
+ unsigned long flags;
+ struct socket *socket;
+ struct task_struct *tcp_rx = NULL;
+ struct task_struct *tcp_tx = NULL;
+ int sockfd = 0;
+
+ spin_lock_irqsave(&ud->lock, flags);
+ if (vdev->ud.in_disconnect) {
+ pr_info("%s: Disconnect in progress for sockfd %d\n",
+ __func__, ud->sockfd);
+ spin_unlock_irqrestore(&ud->lock, flags);
+ return;
+ }
+ vdev->ud.in_disconnect = true;
+ socket = ud->tcp_socket;
+ tcp_rx = vdev->ud.tcp_rx;
+ tcp_tx = vdev->ud.tcp_tx;
+ sockfd = ud->sockfd;
+ spin_unlock_irqrestore(&ud->lock, flags);
/* need this? see stub_dev.c */
- if (ud->tcp_socket) {
- pr_debug("shutdown tcp_socket %d\n", ud->sockfd);
- kernel_sock_shutdown(ud->tcp_socket, SHUT_RDWR);
+ if (socket) {
+ pr_info("%s: shutdown tcp_socket %d\n", __func__, sockfd);
+ kernel_sock_shutdown(socket, SHUT_RDWR);
}
- /* kill threads related to this sdev */
- if (vdev->ud.tcp_rx) {
- kthread_stop_put(vdev->ud.tcp_rx);
- vdev->ud.tcp_rx = NULL;
+ /* kill threads related to this vdev */
+ if (tcp_rx) {
+ pr_info("%s: stop rx thread\n", __func__);
+ kthread_stop_put(tcp_rx);
}
- if (vdev->ud.tcp_tx) {
- kthread_stop_put(vdev->ud.tcp_tx);
- vdev->ud.tcp_tx = NULL;
+ if (tcp_tx) {
+ pr_info("%s: stop tx thread\n", __func__);
+ kthread_stop_put(tcp_tx);
}
- pr_info("stop threads\n");
+ spin_lock_irqsave(&ud->lock, flags);
/* active connection is closed */
- if (vdev->ud.tcp_socket) {
+ if (ud->tcp_socket) {
+ vdev->ud.tcp_rx = NULL;
+ vdev->ud.tcp_tx = NULL;
sockfd_put(vdev->ud.tcp_socket);
vdev->ud.tcp_socket = NULL;
vdev->ud.sockfd = -1;
}
- pr_info("release socket\n");
+ vdev->ud.in_disconnect = false;
+ spin_unlock_irqrestore(&ud->lock, flags);
+ pr_info("%s: release socket\n", __func__);
vhci_device_unlink_cleanup(vdev);
@@ -1057,7 +1080,7 @@ static void vhci_shutdown_connection(struct usbip_device *ud)
*/
rh_port_disconnect(vdev);
- pr_info("disconnect device\n");
+ pr_info("%s: disconnect device\n", __func__);
}
static void vhci_device_reset(struct usbip_device *ud)
@@ -1073,7 +1096,9 @@ static void vhci_device_reset(struct usbip_device *ud)
usb_put_dev(vdev->udev);
vdev->udev = NULL;
- if (ud->tcp_socket) {
+ if (!vdev->ud.in_disconnect && ud->tcp_socket) {
+ pr_info("%s: release tcp_socket %d\n",
+ __func__, ud->sockfd);
sockfd_put(ud->tcp_socket);
ud->tcp_socket = NULL;
ud->sockfd = -1;
diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index c4b4256e5dad..c4457026d5ad 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -412,6 +412,10 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
vdev->ud.tcp_rx = tcp_rx;
vdev->ud.tcp_tx = tcp_tx;
vdev->ud.status = VDEV_ST_NOTASSIGNED;
+
+ /* used to run socket shutdown just once */
+ vdev->ud.in_disconnect = false;
+
usbip_kcov_handle_init(&vdev->ud);
spin_unlock(&vdev->ud.lock);
--
2.27.0
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