[PATCH 5.4 04/54] usb: gadget: f_fs: Use local copy of descriptors for userspace copy

Greg Kroah-Hartman
2020-12-10T18:26:12Z

From: Vamsi Krishna Samavedam <vskrishn@codeaurora.org>

commit a4b98a7512f18534ce33a7e98e49115af59ffa00 upstream.

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>

---
drivers/usb/gadget/function/f_fs.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1328,7 +1328,7 @@ static long ffs_epfile_ioctl(struct file
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:
@@ -1340,10 +1340,12 @@ static long ffs_epfile_ioctl(struct file
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;