[PATCH 3/4] usbip: vudc synchronize sysfs code paths

[Shuah Khan]

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.

Use sysfs_lock to protect sysfs paths in vudc.

Reported-and-tested-by: syzbot+a93fba6d384346a76...@syzkaller.appspotmail.com
Cc: sta...@vger.kernel.org
Signed-off-by: Shuah Khan <sk...@linuxfoundation.org>
---
 drivers/usb/usbip/vudc_dev.c   | 1 +
 drivers/usb/usbip/vudc_sysfs.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/drivers/usb/usbip/vudc_dev.c b/drivers/usb/usbip/vudc_dev.c
index c8eeabdd9b56..2bc428f2e261 100644
--- a/drivers/usb/usbip/vudc_dev.c
+++ b/drivers/usb/usbip/vudc_dev.c
@@ -572,6 +572,7 @@ static int init_vudc_hw(struct vudc *udc)
        init_waitqueue_head(&udc->tx_waitq);
 
        spin_lock_init(&ud->lock);
+       mutex_init(&ud->sysfs_lock);
        ud->status = SDEV_ST_AVAILABLE;
        ud->side = USBIP_VUDC;
 
diff --git a/drivers/usb/usbip/vudc_sysfs.c b/drivers/usb/usbip/vudc_sysfs.c
index 7383a543c6d1..f7633ee655a1 100644
--- a/drivers/usb/usbip/vudc_sysfs.c
+++ b/drivers/usb/usbip/vudc_sysfs.c
@@ -112,6 +112,7 @@ static ssize_t usbip_sockfd_store(struct device *dev,
                dev_err(dev, "no device");
                return -ENODEV;
        }
+       mutex_lock(&udc->ud.sysfs_lock);
        spin_lock_irqsave(&udc->lock, flags);
        /* Don't export what we don't have */
        if (!udc->driver || !udc->pullup) {
@@ -187,6 +188,8 @@ static ssize_t usbip_sockfd_store(struct device *dev,
 
                wake_up_process(udc->ud.tcp_rx);
                wake_up_process(udc->ud.tcp_tx);
+
+               mutex_unlock(&udc->ud.sysfs_lock);
                return count;
 
        } else {
@@ -207,6 +210,7 @@ static ssize_t usbip_sockfd_store(struct device *dev,
        }
 
        spin_unlock_irqrestore(&udc->lock, flags);
+       mutex_unlock(&udc->ud.sysfs_lock);
 
        return count;
 
@@ -216,6 +220,7 @@ static ssize_t usbip_sockfd_store(struct device *dev,
        spin_unlock_irq(&udc->ud.lock);
 unlock:
        spin_unlock_irqrestore(&udc->lock, flags);
+       mutex_unlock(&udc->ud.sysfs_lock);
 
        return ret;
 }
-- 
2.27.0