staging: comedi: ni_usb6501: Fix possible double-free of ->usb_rx_buf
authorIan Abbott <abbotti@mev.co.uk>
Mon, 15 Apr 2019 11:43:02 +0000 (12:43 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 17 Apr 2019 09:59:24 +0000 (11:59 +0200)
commitaf4b54a2e5ba18259ff9aac445bf546dd60d037e
treebfe50b627896c0c1943ff1aabd1e412e982a0430
parent660cf4ce9d0f3497cc7456eaa6d74c8b71d6282c
staging: comedi: ni_usb6501: Fix possible double-free of ->usb_rx_buf

`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>
drivers/staging/comedi/drivers/ni_usb6501.c