usb: gadget: f_fs: Use local copy of descriptors for userspace copy

The function may be unbound causing the ffs_ep and its descriptors
to be freed while userspace is in the middle of an ioctl requesting
the same descriptors. Avoid dangling pointer reference by first
making a local copy of desctiptors before releasing the spinlock.

Fixes: c559a3534109 ("usb: gadget: f_fs: add ioctl returning ep descriptor")
Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Vamsi Krishna Samavedam <vskrishn@codeaurora.org>
Signed-off-by: Jack Pham <jackp@codeaurora.org>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201130203453.28154-1-jackp@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 046f770..c727cb5 100644 (file)
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1324,7 +1324,7 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
        case FUNCTIONFS_ENDPOINT_DESC:
        {
                int desc_idx;
-               struct usb_endpoint_descriptor *desc;
+               struct usb_endpoint_descriptor desc1, *desc;
 
                switch (epfile->ffs->gadget->speed) {
                case USB_SPEED_SUPER:
@@ -1336,10 +1336,12 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
                default:
                        desc_idx = 0;
                }
+
                desc = epfile->ep->descs[desc_idx];
+               memcpy(&desc1, desc, desc->bLength);
 
                spin_unlock_irq(&epfile->ffs->eps_lock);
-               ret = copy_to_user((void __user *)value, desc, desc->bLength);
+               ret = copy_to_user((void __user *)value, &desc1, desc1.bLength);
                if (ret)
                        ret = -EFAULT;
                return ret;