diff mbox series

[v4,02/12] usb: usbip: vhci: serialize attach_store()/detach_store() against event_handler()

Message ID 20210304152455.3685-3-penguin-kernel@I-love.SAKURA.ne.jp
State New
Headers show
Series usb: usbip: serialize attach/detach operations | expand

Commit Message

Tetsuo Handa March 4, 2021, 3:24 p.m. UTC 
syzbot is reporting a NULL pointer dereference at sock_sendmsg() [1], for
lack of serialization between attach_store() and event_handler() causes
vhci_shutdown_connection() to observe vdev->ud.tcp_tx == NULL while
vdev->ud.tcp_socket != NULL. Please read the reference link for details of
this race window.

Since I don't want to replace "return" with "goto" in order to call
usbip_event_unlock(), wrap whole functions in order to keep changes
minimal.

[1] https://syzkaller.appspot.com/bug?extid=95ce4b142579611ef0a9

Reported-by: syzbot <syzbot+95ce4b142579611ef0a9@syzkaller.appspotmail.com>
Tested-by: syzbot <syzbot+a93fba6d384346a761e3@syzkaller.appspotmail.com>
References: https://lkml.kernel.org/r/676d4518-0faa-9fab-15db-0db8d216d7fb@i-love.sakura.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
 drivers/usb/usbip/vhci_sysfs.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index 96e5371dc335..031e21aad96a 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -225,8 +225,8 @@  static int valid_port(__u32 *pdev_nr, __u32 *rhport)
 	return 1;
 }
 
-static ssize_t detach_store(struct device *dev, struct device_attribute *attr,
-			    const char *buf, size_t count)
+static ssize_t __detach_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
 {
 	__u32 port = 0, pdev_nr = 0, rhport = 0;
 	struct usb_hcd *hcd;
@@ -263,6 +263,17 @@  static ssize_t detach_store(struct device *dev, struct device_attribute *attr,
 
 	return count;
 }
+static ssize_t detach_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	ssize_t ret = usbip_event_lock_killable();
+
+	if (ret)
+		return ret;
+	ret = __detach_store(dev, attr, buf, count);
+	usbip_event_unlock();
+	return ret;
+}
 static DEVICE_ATTR_WO(detach);
 
 static int valid_args(__u32 *pdev_nr, __u32 *rhport,
@@ -300,8 +311,8 @@  static int valid_args(__u32 *pdev_nr, __u32 *rhport,
  *
  * write() returns 0 on success, else negative errno.
  */
-static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
-			    const char *buf, size_t count)
+static ssize_t __attach_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t count)
 {
 	struct socket *socket;
 	int sockfd = 0;
@@ -396,6 +407,17 @@  static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
 
 	return count;
 }
+static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	ssize_t ret = usbip_event_lock_killable();
+
+	if (ret)
+		return ret;
+	ret = __attach_store(dev, attr, buf, count);
+	usbip_event_unlock();
+	return ret;
+}
 static DEVICE_ATTR_WO(attach);
 
 #define MAX_STATUS_NAME 16