[lkml]   [2019]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 4.9 26/44] staging: comedi: ni_usb6501: Fix possible double-free of ->usb_rx_buf
From: Ian Abbott <>

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 <>
Cc: stable <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/staging/comedi/drivers/ni_usb6501.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

--- a/drivers/staging/comedi/drivers/ni_usb6501.c
+++ b/drivers/staging/comedi/drivers/ni_usb6501.c
@@ -472,10 +472,8 @@ static int ni6501_alloc_usb_buffers(stru

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;

 \ /
  Last update: 2019-04-24 19:59    [W:0.301 / U:1.896 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site