Commit 9ae4c50f authored Apr 15, 2019 by Ian Abbott Committed by Greg Kroah-Hartman Apr 27, 2019

staging: comedi: ni_usb6501: Fix possible double-free of ->usb_rx_buf



commit af4b54a2e5ba18259ff9aac445bf546dd60d037e upstream.

`ni6501_alloc_usb_buffers()` is called from `ni6501_auto_attach()` to
allocate RX and TX buffers for USB transfers.  It allocates
`devpriv->usb_rx_buf` followed by `devpriv->usb_tx_buf`.  If the
allocation of `devpriv->usb_tx_buf` fails, it frees
`devpriv->usb_rx_buf`, leaving the pointer set dangling, and returns an
error.  Later, `ni6501_detach()` will be called from the core comedi
module code to clean up.  `ni6501_detach()` also frees both
`devpriv->usb_rx_buf` and `devpriv->usb_tx_buf`, but
`devpriv->usb_rx_buf` may have already beed freed, leading to a
double-free error.  Fix it bu removing the call to
`kfree(devpriv->usb_rx_buf)` from `ni6501_alloc_usb_buffers()`, relying
on `ni6501_detach()` to free the memory.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 72cd1a32

drivers/staging/comedi/drivers/ni_usb6501.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -472,10 +472,8 @@ static int ni6501_alloc_usb_buffers(struct comedi_device *dev)

		size = usb_endpoint_maxp(devpriv->ep_tx);
		devpriv->usb_tx_buf = kzalloc(size, GFP_KERNEL);
		if (!devpriv->usb_tx_buf) {
		kfree(devpriv->usb_rx_buf);
		if (!devpriv->usb_tx_buf)
		return -ENOMEM;
		}

		return 0;
		}