On 08/12/16 11:34, SF Markus Elfring wrote:
From: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 8 Dec 2016 10:01:54 +0100
The functions "kcalloc" and "kzalloc" were called in four cases by the
function "usbdux_alloc_usb_buffers" without checking immediately
if they succeded.
This issue was detected by using the Coccinelle software.
Allocated memory was also not released if one of these function
calls failed.
* Split a condition check for memory allocation failures.
* Add more exception handling.
Fixes: ef1e3c4a3b383c6da3979670fcb5c6e9c7de4741 ("staging: comedi: usbdux: tidy up usbdux_alloc_usb_buffers()")
Signed-off-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
---
drivers/staging/comedi/drivers/usbdux.c | 53 ++++++++++++++++++++++++++-------
1 file changed, 43 insertions(+), 10 deletions(-)
diff --git a/drivers/staging/comedi/drivers/usbdux.c b/drivers/staging/comedi/drivers/usbdux.c
index f4f05d29d30d..d7d683bd669c 100644
--- a/drivers/staging/comedi/drivers/usbdux.c
+++ b/drivers/staging/comedi/drivers/usbdux.c
@@ -1449,24 +1449,35 @@ static int usbdux_alloc_usb_buffers(struct comedi_device *dev)
struct usb_device *usb = comedi_to_usb_dev(dev);
struct usbdux_private *devpriv = dev->private;
struct urb *urb;
- int i;
+ int i, x;
devpriv->dux_commands = kzalloc(SIZEOFDUXBUFFER, GFP_KERNEL);
+ if (!devpriv->dux_commands)
+ return -ENOMEM;
+
devpriv->in_buf = kzalloc(SIZEINBUF, GFP_KERNEL);
+ if (!devpriv->in_buf)
+ goto free_commands;
+
devpriv->insn_buf = kzalloc(SIZEINSNBUF, GFP_KERNEL);
+ if (!devpriv->insn_buf)
+ goto free_in_buf;
+
devpriv->ai_urbs = kcalloc(devpriv->n_ai_urbs, sizeof(void *),
GFP_KERNEL);
+ if (!devpriv->ai_urbs)
+ goto free_insn_buf;
+
devpriv->ao_urbs = kcalloc(devpriv->n_ao_urbs, sizeof(void *),
GFP_KERNEL);
- if (!devpriv->dux_commands || !devpriv->in_buf || !devpriv->insn_buf ||
- !devpriv->ai_urbs || !devpriv->ao_urbs)
- return -ENOMEM;
+ if (!devpriv->ao_urbs)
+ goto free_ai_urbs;
for (i = 0; i < devpriv->n_ai_urbs; i++) {
/* one frame: 1ms */
urb = usb_alloc_urb(1, GFP_KERNEL);
if (!urb)
- return -ENOMEM;
+ goto free_n_ai_urbs;
devpriv->ai_urbs[i] = urb;
urb->dev = usb;
@@ -1475,7 +1486,7 @@ static int usbdux_alloc_usb_buffers(struct comedi_device *dev)
urb->transfer_flags = URB_ISO_ASAP;
urb->transfer_buffer = kzalloc(SIZEINBUF, GFP_KERNEL);
if (!urb->transfer_buffer)
- return -ENOMEM;
+ goto free_n_ai_urbs;
urb->complete = usbduxsub_ai_isoc_irq;
urb->number_of_packets = 1;
@@ -1488,7 +1499,7 @@ static int usbdux_alloc_usb_buffers(struct comedi_device *dev)
/* one frame: 1ms */
urb = usb_alloc_urb(1, GFP_KERNEL);
if (!urb)
- return -ENOMEM;
+ goto free_n_ao_urbs;
devpriv->ao_urbs[i] = urb;
urb->dev = usb;
@@ -1497,7 +1508,7 @@ static int usbdux_alloc_usb_buffers(struct comedi_device *dev)
urb->transfer_flags = URB_ISO_ASAP;
urb->transfer_buffer = kzalloc(SIZEOUTBUF, GFP_KERNEL);
if (!urb->transfer_buffer)
- return -ENOMEM;
+ goto free_n_ao_urbs;
urb->complete = usbduxsub_ao_isoc_irq;
urb->number_of_packets = 1;
@@ -1514,17 +1525,39 @@ static int usbdux_alloc_usb_buffers(struct comedi_device *dev)
if (devpriv->pwm_buf_sz) {
urb = usb_alloc_urb(0, GFP_KERNEL);
if (!urb)
- return -ENOMEM;
+ goto free_n_ao_urbs;
devpriv->pwm_urb = urb;
/* max bulk ep size in high speed */
urb->transfer_buffer = kzalloc(devpriv->pwm_buf_sz,
GFP_KERNEL);
if (!urb->transfer_buffer)
- return -ENOMEM;
+ goto free_pwm_urb;
}
return 0;
+free_pwm_urb:
+ usb_free_urb(urb);
+free_n_ao_urbs:
+ for (x = 0; x < i; ++x) {
+ kfree(devpriv->ao_urbs[x]->transfer_buffer);
+ usb_free_urb(devpriv->ao_urbs[x]);
+ }
+free_n_ai_urbs:
+ for (x = 0; x < i; ++x) {
+ kfree(devpriv->ai_urbs[x]->transfer_buffer);
+ usb_free_urb(devpriv->ai_urbs[x]);
+ }
+ kfree(devpriv->ao_urbs);
+free_ai_urbs:
+ kfree(devpriv->ai_urbs);
+free_insn_buf:
+ kfree(devpriv->insn_buf);
+free_in_buf:
+ kfree(devpriv->in_buf);
+free_commands:
+ kfree(devpriv->dux_commands);
+ return -ENOMEM;
}
static void usbdux_free_usb_buffers(struct comedi_device *dev)
Actually, the original code worked fine, and these changes will result
in an Oops if the allocations fail. I'll explain why, since it isn't
obvious without some knowledge of the clean-up strategy used by comedi
drivers:
1. usbdux_alloc_usb_buffers() is called from usbdux_auto_attach().
2. usbdux_auto_attach() will return an error if
usbdux_alloc_usb_buffers() fails.
3. If usbdux_auto_attach() returns an error to the core comedi module,
the core comedi module will call usbdux_detach().
4. usbdux_detach() calls usbdux_free_usb_buffers().
5. usbdux_free_usb_buffers() frees any of the buffers that were
successfully allocated by usbdux_alloc_usb_buffers().
The net result is that devpriv->dux_commands and the others will be
passed to kfree() twice, leading to the oops. That could be prevented
by settting devpriv->dux_commands and the others to NULL in the error
handling of usbdux_alloc_usb_buffers(), but it really isn't necessary as
the existing code works, and all the other comedi drivers follow the
same strategy of leaving clean-up to their comedi 'detach' handler.
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Web: http://www.mev.co.uk/ )=-
--
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