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staging: comedi: vmk80xx: Fix possible double-free of ->usb_rx_buf 

`vmk80xx_alloc_usb_buffers()` is called from `vmk80xx_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, `vmk80xx_detach()` will be called from the core comedi
module code to clean up.  `vmk80xx_detach()` also frees both
`devpriv->usb_rx_buf` and `devpriv->usb_tx_buf`, but
`devpriv->usb_rx_buf` may have already been freed, leading to a
double-free error.  Fix it by removing the call to
`kfree(devpriv->usb_rx_buf)` from `vmk80xx_alloc_usb_buffers()`, relying
on `vmk80xx_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>
This commit is contained in:
Ian Abbott 2019-04-15 12:52:30 +01:00 committed by Greg Kroah-Hartman
parent 08b7c2f920
commit 663d294b47
1 changed files with 1 additions and 3 deletions
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4
drivers/staging/comedi/drivers/vmk80xx.c
View File

@ -682,10 +682,8 @@ static int vmk80xx_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;
}