queue-4.14/staging-comedi-ni_usb6501-fix-possible-double-free-of-usb_rx_buf.patch

   1 From af4b54a2e5ba18259ff9aac445bf546dd60d037e Mon Sep 17 00:00:00 2001
   2 From: Ian Abbott <abbotti@mev.co.uk>
   3 Date: Mon, 15 Apr 2019 12:43:02 +0100
   4 Subject: staging: comedi: ni_usb6501: Fix possible double-free of ->usb_rx_buf
   5
   6 From: Ian Abbott <abbotti@mev.co.uk>
   7
   8 commit af4b54a2e5ba18259ff9aac445bf546dd60d037e upstream.
   9
  10 `ni6501_alloc_usb_buffers()` is called from `ni6501_auto_attach()` to
  11 allocate RX and TX buffers for USB transfers.  It allocates
  12 `devpriv->usb_rx_buf` followed by `devpriv->usb_tx_buf`.  If the
  13 allocation of `devpriv->usb_tx_buf` fails, it frees
  14 `devpriv->usb_rx_buf`, leaving the pointer set dangling, and returns an
  15 error.  Later, `ni6501_detach()` will be called from the core comedi
  16 module code to clean up.  `ni6501_detach()` also frees both
  17 `devpriv->usb_rx_buf` and `devpriv->usb_tx_buf`, but
  18 `devpriv->usb_rx_buf` may have already beed freed, leading to a
  19 double-free error.  Fix it bu removing the call to
  20 `kfree(devpriv->usb_rx_buf)` from `ni6501_alloc_usb_buffers()`, relying
  21 on `ni6501_detach()` to free the memory.
  22
  23 Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
  24 Cc: stable <stable@vger.kernel.org>
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26
  27 ---
  28  drivers/staging/comedi/drivers/ni_usb6501.c |    4 +---
  29  1 file changed, 1 insertion(+), 3 deletions(-)
  30
  31 --- a/drivers/staging/comedi/drivers/ni_usb6501.c
  32 +++ b/drivers/staging/comedi/drivers/ni_usb6501.c
  33 @@ -472,10 +472,8 @@ static int ni6501_alloc_usb_buffers(stru
  34
  35         size = usb_endpoint_maxp(devpriv->ep_tx);
  36         devpriv->usb_tx_buf = kzalloc(size, GFP_KERNEL);
  37 -       if (!devpriv->usb_tx_buf) {
  38 -               kfree(devpriv->usb_rx_buf);
  39 +       if (!devpriv->usb_tx_buf)
  40                 return -ENOMEM;
  41 -       }
  42
  43         return 0;
  44  }