usbip: add sysfs_lock to synchronize sysfs code paths

commit 4e9c93af7279b059faf5bb1897ee90512b258a12 upstream.

Fuzzing uncovered race condition between sysfs code paths in usbip
drivers. Device connect/disconnect code paths initiated through
sysfs interface are prone to races if disconnect happens during
connect and vice versa.

This problem is common to all drivers while it can be reproduced easily
in vhci_hcd. Add a sysfs_lock to usbip_device struct to protect the paths.

Use this in vhci_hcd to protect sysfs paths. For a complete fix, usip_host
and usip-vudc drivers and the event handler will have to use this lock to
protect the paths. These changes will be done in subsequent patches.

Cc: stable@vger.kernel.org
Reported-and-tested-by: syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/b6568f7beae702bbc236a545d3c020106ca75eac.1616807117.git.skhan@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/usbip/usbip_common.h b/drivers/usb/usbip/usbip_common.h
index 8be857a4fa132fc1e48d86bfb1f08f9f4fef7202..a7e6ce96f62c7753111a7115a5808d66182f6f50 100644 (file)
--- a/drivers/usb/usbip/usbip_common.h
+++ b/drivers/usb/usbip/usbip_common.h
@@ -263,6 +263,9 @@ struct usbip_device {
        /* lock for status */
        spinlock_t lock;
 
+       /* mutex for synchronizing sysfs store paths */
+       struct mutex sysfs_lock;
+
        int sockfd;
        struct socket *tcp_socket;
 

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index a20a8380ca0c97ab318153e0373333e356f95317..4ba6bcdaa8e9d49b972d7aa608ad9cc7bcd1233c 100644 (file)
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c
@@ -1101,6 +1101,7 @@ static void vhci_device_init(struct vhci_device *vdev)
        vdev->ud.side   = USBIP_VHCI;
        vdev->ud.status = VDEV_ST_NULL;
        spin_lock_init(&vdev->ud.lock);
+       mutex_init(&vdev->ud.sysfs_lock);
 
        INIT_LIST_HEAD(&vdev->priv_rx);
        INIT_LIST_HEAD(&vdev->priv_tx);

diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index e64ea314930be5d553aca579b6cbd7bf8d135b4d..ebc7be1d982074bc45619f0deba6cfead536c73b 100644 (file)
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -185,6 +185,8 @@ static int vhci_port_disconnect(struct vhci_hcd *vhci_hcd, __u32 rhport)
 
        usbip_dbg_vhci_sysfs("enter\n");
 
+       mutex_lock(&vdev->ud.sysfs_lock);
+
        /* lock */
        spin_lock_irqsave(&vhci->lock, flags);
        spin_lock(&vdev->ud.lock);
@@ -195,6 +197,7 @@ static int vhci_port_disconnect(struct vhci_hcd *vhci_hcd, __u32 rhport)
                /* unlock */
                spin_unlock(&vdev->ud.lock);
                spin_unlock_irqrestore(&vhci->lock, flags);
+               mutex_unlock(&vdev->ud.sysfs_lock);
 
                return -EINVAL;
        }
@@ -205,6 +208,8 @@ static int vhci_port_disconnect(struct vhci_hcd *vhci_hcd, __u32 rhport)
 
        usbip_event_add(&vdev->ud, VDEV_EVENT_DOWN);
 
+       mutex_unlock(&vdev->ud.sysfs_lock);
+
        return 0;
 }
 
@@ -349,30 +354,36 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
        else
                vdev = &vhci->vhci_hcd_hs->vdev[rhport];
 
+       mutex_lock(&vdev->ud.sysfs_lock);
+
        /* Extract socket from fd. */
        socket = sockfd_lookup(sockfd, &err);
        if (!socket) {
                dev_err(dev, "failed to lookup sock");
-               return -EINVAL;
+               err = -EINVAL;
+               goto unlock_mutex;
        }
        if (socket->type != SOCK_STREAM) {
                dev_err(dev, "Expecting SOCK_STREAM - found %d",
                        socket->type);
                sockfd_put(socket);
-               return -EINVAL;
+               err = -EINVAL;
+               goto unlock_mutex;
        }
 
        /* create threads before locking */
        tcp_rx = kthread_create(vhci_rx_loop, &vdev->ud, "vhci_rx");
        if (IS_ERR(tcp_rx)) {
                sockfd_put(socket);
-               return -EINVAL;
+               err = -EINVAL;
+               goto unlock_mutex;
        }
        tcp_tx = kthread_create(vhci_tx_loop, &vdev->ud, "vhci_tx");
        if (IS_ERR(tcp_tx)) {
                kthread_stop(tcp_rx);
                sockfd_put(socket);
-               return -EINVAL;
+               err = -EINVAL;
+               goto unlock_mutex;
        }
 
        /* get task structs now */
@@ -397,7 +408,8 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
                 * Will be retried from userspace
                 * if there's another free port.
                 */
-               return -EBUSY;
+               err = -EBUSY;
+               goto unlock_mutex;
        }
 
        dev_info(dev, "pdev(%u) rhport(%u) sockfd(%d)\n",
@@ -422,7 +434,15 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 
        rh_port_connect(vdev, speed);
 
+       dev_info(dev, "Device attached\n");
+
+       mutex_unlock(&vdev->ud.sysfs_lock);
+
        return count;
+
+unlock_mutex:
+       mutex_unlock(&vdev->ud.sysfs_lock);
+       return err;
 }
 static DEVICE_ATTR_WO(attach);