[PATCH v2] usb: iowarrior: replace kmalloc with kmalloc_array

[PATCH v2] usb: iowarrior: replace kmalloc with kmalloc_array

[Gustavo A. R. Silva]

A common flaw in the kernel is integer overflow during memory allocation
size calculations. In an effort to reduce the frequency of these bugs,
kmalloc_array was implemented, which allocates memory for an array,
while at the same time detects integer overflow.

This patch replaces cases of:

kmalloc(a * b, gfp)

with:
	kmalloc_array(a * b, gfp)

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
Changes in v2:
 - Align GFP_KERNEL to open parenthesis.

 drivers/usb/misc/iowarrior.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/misc/iowarrior.c b/drivers/usb/misc/iowarrior.c
index c2991b8..ba05dd8 100644
--- a/drivers/usb/misc/iowarrior.c
+++ b/drivers/usb/misc/iowarrior.c
@@ -808,8 +808,8 @@ static int iowarrior_probe(struct usb_interface *interface,
 			 dev->int_in_endpoint->bInterval);
 	/* create an internal buffer for interrupt data from the device */
 	dev->read_queue =
-	    kmalloc(((dev->report_size + 1) * MAX_INTERRUPT_BUFFER),
-		    GFP_KERNEL);
+	    kmalloc_array(dev->report_size + 1, MAX_INTERRUPT_BUFFER,
+			  GFP_KERNEL);
 	if (!dev->read_queue)
 		goto error;
 	/* Get the serial-number of the chip */
-- 
2.7.4

Re: [PATCH v2] usb: iowarrior: replace kmalloc with kmalloc_array

[Oliver Neukum]

On Do, 2018-08-23 at 12:44 -0500,  Gustavo A. R. Silva  wrote:
> A common flaw in the kernel is integer overflow during memory allocation
> size calculations. In an effort to reduce the frequency of these bugs,
> kmalloc_array was implemented, which allocates memory for an array,
> while at the same time detects integer overflow.
> 
> This patch replaces cases of:
> 
> kmalloc(a * b, gfp)
> 
> with:
> 	kmalloc_array(a * b, gfp)

I am afraid there is a problem here. The driver currently is a gross
violation of the DMA rules. Unfortunately your patch does not fix that.

That is on anyrhing other than x86 you cannot take the size of a
report,
but you must use the size of a cache line.

	Regards
		Oliver