HID: usbhid: Fix race between usbhid_close() and usbhid_stop()

The syzbot fuzzer discovered a bad race between in the usbhid driver
between usbhid_stop() and usbhid_close().  In particular,
usbhid_stop() does:

	usb_free_urb(usbhid->urbin);
	...
	usbhid->urbin = NULL; /* don't mess up next start */

and usbhid_close() does:

	usb_kill_urb(usbhid->urbin);

with no mutual exclusion.  If the two routines happen to run
concurrently so that usb_kill_urb() is called in between the
usb_free_urb() and the NULL assignment, it will access the
deallocated urb structure -- a use-after-free bug.

This patch adds a mutex to the usbhid private structure and uses it to
enforce mutual exclusion of the usbhid_start(), usbhid_stop(),
usbhid_open() and usbhid_close() callbacks.

Reported-and-tested-by: syzbot+7bf5a7b0f0a1f9446f4c@syzkaller.appspotmail.com
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index c7bc9db..17a638f 100644 (file)
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -682,16 +682,21 @@ static int usbhid_open(struct hid_device *hid)
        struct usbhid_device *usbhid = hid->driver_data;
        int res;
 
+       mutex_lock(&usbhid->mutex);
+
        set_bit(HID_OPENED, &usbhid->iofl);
 
-       if (hid->quirks & HID_QUIRK_ALWAYS_POLL)
-               return 0;
+       if (hid->quirks & HID_QUIRK_ALWAYS_POLL) {
+               res = 0;
+               goto Done;
+       }
 
        res = usb_autopm_get_interface(usbhid->intf);
        /* the device must be awake to reliably request remote wakeup */
        if (res < 0) {
                clear_bit(HID_OPENED, &usbhid->iofl);
-               return -EIO;
+               res = -EIO;
+               goto Done;
        }
 
        usbhid->intf->needs_remote_wakeup = 1;
@@ -725,6 +730,9 @@ static int usbhid_open(struct hid_device *hid)
                msleep(50);
 
        clear_bit(HID_RESUME_RUNNING, &usbhid->iofl);
+
+ Done:
+       mutex_unlock(&usbhid->mutex);
        return res;
 }
 
@@ -732,6 +740,8 @@ static void usbhid_close(struct hid_device *hid)
 {
        struct usbhid_device *usbhid = hid->driver_data;
 
+       mutex_lock(&usbhid->mutex);
+
        /*
         * Make sure we don't restart data acquisition due to
         * a resumption we no longer care about by avoiding racing
@@ -743,12 +753,13 @@ static void usbhid_close(struct hid_device *hid)
                clear_bit(HID_IN_POLLING, &usbhid->iofl);
        spin_unlock_irq(&usbhid->lock);
 
-       if (hid->quirks & HID_QUIRK_ALWAYS_POLL)
-               return;
+       if (!(hid->quirks & HID_QUIRK_ALWAYS_POLL)) {
+               hid_cancel_delayed_stuff(usbhid);
+               usb_kill_urb(usbhid->urbin);
+               usbhid->intf->needs_remote_wakeup = 0;
+       }
 
-       hid_cancel_delayed_stuff(usbhid);
-       usb_kill_urb(usbhid->urbin);
-       usbhid->intf->needs_remote_wakeup = 0;
+       mutex_unlock(&usbhid->mutex);
 }
 
 /*
@@ -1057,6 +1068,8 @@ static int usbhid_start(struct hid_device *hid)
        unsigned int n, insize = 0;
        int ret;
 
+       mutex_lock(&usbhid->mutex);
+
        clear_bit(HID_DISCONNECTED, &usbhid->iofl);
 
        usbhid->bufsize = HID_MIN_BUFFER_SIZE;
@@ -1177,6 +1190,8 @@ static int usbhid_start(struct hid_device *hid)
                usbhid_set_leds(hid);
                device_set_wakeup_enable(&dev->dev, 1);
        }
+
+       mutex_unlock(&usbhid->mutex);
        return 0;
 
 fail:
@@ -1187,6 +1202,7 @@ fail:
        usbhid->urbout = NULL;
        usbhid->urbctrl = NULL;
        hid_free_buffers(dev, hid);
+       mutex_unlock(&usbhid->mutex);
        return ret;
 }
 
@@ -1202,6 +1218,8 @@ static void usbhid_stop(struct hid_device *hid)
                usbhid->intf->needs_remote_wakeup = 0;
        }
 
+       mutex_lock(&usbhid->mutex);
+
        clear_bit(HID_STARTED, &usbhid->iofl);
        spin_lock_irq(&usbhid->lock);   /* Sync with error and led handlers */
        set_bit(HID_DISCONNECTED, &usbhid->iofl);
@@ -1222,6 +1240,8 @@ static void usbhid_stop(struct hid_device *hid)
        usbhid->urbout = NULL;
 
        hid_free_buffers(hid_to_usb_dev(hid), hid);
+
+       mutex_unlock(&usbhid->mutex);
 }
 
 static int usbhid_power(struct hid_device *hid, int lvl)
@@ -1382,6 +1402,7 @@ static int usbhid_probe(struct usb_interface *intf, const struct usb_device_id *
        INIT_WORK(&usbhid->reset_work, hid_reset);
        timer_setup(&usbhid->io_retry, hid_retry_timeout, 0);
        spin_lock_init(&usbhid->lock);
+       mutex_init(&usbhid->mutex);
 
        ret = hid_add_device(hid);
        if (ret) {

diff --git a/drivers/hid/usbhid/usbhid.h b/drivers/hid/usbhid/usbhid.h
index 8620408..75fe85d 100644 (file)
--- a/drivers/hid/usbhid/usbhid.h
+++ b/drivers/hid/usbhid/usbhid.h
@@ -80,6 +80,7 @@ struct usbhid_device {
        dma_addr_t outbuf_dma;                                          /* Output buffer dma */
        unsigned long last_out;                                                 /* record of last output for timeouts */
 
+       struct mutex mutex;                                             /* start/stop/open/close */
        spinlock_t lock;                                                /* fifo spinlock */
        unsigned long iofl;                                             /* I/O flags (CTRL_RUNNING, OUT_RUNNING) */
        struct timer_list io_retry;                                     /* Retry timer */