USB: core: Fix access violation during port device removal

commit a4b46d450c49f32e9d4247b421e58083fde304ce upstream.

Testing with KASAN and syzkaller revealed a bug in port.c:disable_store():
usb_hub_to_struct_hub() can return NULL if the hub that the port belongs to
is concurrently removed, but the function does not check for this
possibility before dereferencing the returned value.

It turns out that the first dereference is unnecessary, since hub->intfdev
is the parent of the port device, so it can be changed easily.  Adding a
check for hub == NULL prevents further problems.

The same bug exists in the disable_show() routine, and it can be fixed the
same way.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Yue Sun <samsun1006219@gmail.com>
Reported-by: xingwei lee <xrivendell7@gmail.com>
Link: https://lore.kernel.org/linux-usb/CAEkJfYON+ry7xPx=AiLR9jzUNT+i_Va68ACajOC3HoacOfL1ig@mail.gmail.com/
Fixes: f061f43d7418 ("usb: hub: port: add sysfs entry to switch port power")
CC: Michael Grzeschik <m.grzeschik@pengutronix.de>
CC: stable@vger.kernel.org
Link: https://lore.kernel.org/r/393aa580-15a5-44ca-ad3b-6462461cd313@rowland.harvard.edu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 97ff2073cf1e27c2cef83660ec3465043bfd10be..d34d67fcb47b27da5a0ee335a7459fb31f5c20b7 100644 (file)
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -50,13 +50,15 @@ static ssize_t disable_show(struct device *dev,
        struct usb_port *port_dev = to_usb_port(dev);
        struct usb_device *hdev = to_usb_device(dev->parent->parent);
        struct usb_hub *hub = usb_hub_to_struct_hub(hdev);
-       struct usb_interface *intf = to_usb_interface(hub->intfdev);
+       struct usb_interface *intf = to_usb_interface(dev->parent);
        int port1 = port_dev->portnum;
        u16 portstatus, unused;
        bool disabled;
        int rc;
        struct kernfs_node *kn;
 
+       if (!hub)
+               return -ENODEV;
        hub_get(hub);
        rc = usb_autopm_get_interface(intf);
        if (rc < 0)
@@ -100,12 +102,14 @@ static ssize_t disable_store(struct device *dev, struct device_attribute *attr,
        struct usb_port *port_dev = to_usb_port(dev);
        struct usb_device *hdev = to_usb_device(dev->parent->parent);
        struct usb_hub *hub = usb_hub_to_struct_hub(hdev);
-       struct usb_interface *intf = to_usb_interface(hub->intfdev);
+       struct usb_interface *intf = to_usb_interface(dev->parent);
        int port1 = port_dev->portnum;
        bool disabled;
        int rc;
        struct kernfs_node *kn;
 
+       if (!hub)
+               return -ENODEV;
        rc = kstrtobool(buf, &disabled);
        if (rc)
                return rc;