Re: [PATCH] drivers/usb/host/imx21-hcd.c: fix divide-by-zero in func nonisoc_etd_done

[gre...@linuxfoundation.org]

On Wed, Jun 05, 2019 at 02:02:40AM +, Duyanlin wrote:
> 
> If the function usb_maxpacket(urb->dev, urb->pipe, usb_pipeout(urb->pipe)) 
> returns 0, that will cause a illegal divide-by-zero operation, unexpected 
> results may occur.
> It is best to ensure that the denominator is non-zero before dividing by zero.

Please wrap your changelog comments at 72 columns.

> Signed-off-by: Yanlin Du 

This name HAS to match the From: line of your email.  For that reason
alone I can not take this patch.

> ---
>  drivers/usb/host/imx21-hcd.c | 7 ---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/host/imx21-hcd.c b/drivers/usb/host/imx21-hcd.c 
> index 6e3dad1..6a47f78 100644
> --- a/drivers/usb/host/imx21-hcd.c
> +++ b/drivers/usb/host/imx21-hcd.c
> @@ -1038,6 +1038,7 @@ static void nonisoc_etd_done(struct usb_hcd *hcd, int 
> etd_num)
>   int cc;
>   u32 bytes_xfrd;
>   int etd_done;
> + unsigned int maxp;
>  
>   disactivate_etd(imx21, etd_num);
>  
> @@ -1104,13 +1105,13 @@ static void nonisoc_etd_done(struct usb_hcd *hcd, int 
> etd_num)
>   break;
>  
>   case PIPE_BULK:
> + maxp = usb_maxpacket(urb->dev, urb->pipe,
> + usb_pipeout(urb->pipe));

How can this ever be 0?  Don't we abort a lot earlier if a pipe length
is 0?

thanks,

greg k-h

[PATCH] drivers/usb/host/imx21-hcd.c: fix divide-by-zero in func nonisoc_etd_done

[Duyanlin]

If the function usb_maxpacket(urb->dev, urb->pipe, usb_pipeout(urb->pipe)) 
returns 0, that will cause a illegal divide-by-zero operation, unexpected 
results may occur.
It is best to ensure that the denominator is non-zero before dividing by zero.

Signed-off-by: Yanlin Du 
---
 drivers/usb/host/imx21-hcd.c | 7 ---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/host/imx21-hcd.c b/drivers/usb/host/imx21-hcd.c index 
6e3dad1..6a47f78 100644
--- a/drivers/usb/host/imx21-hcd.c
+++ b/drivers/usb/host/imx21-hcd.c
@@ -1038,6 +1038,7 @@ static void nonisoc_etd_done(struct usb_hcd *hcd, int 
etd_num)
int cc;
u32 bytes_xfrd;
int etd_done;
+   unsigned int maxp;
 
disactivate_etd(imx21, etd_num);
 
@@ -1104,13 +1105,13 @@ static void nonisoc_etd_done(struct usb_hcd *hcd, int 
etd_num)
break;
 
case PIPE_BULK:
+   maxp = usb_maxpacket(urb->dev, urb->pipe,
+   usb_pipeout(urb->pipe));
urb->actual_length += bytes_xfrd;
if ((urb_priv->state == US_BULK)
&& (urb->transfer_flags & URB_ZERO_PACKET)
&& urb->transfer_buffer_length > 0
-   && ((urb->transfer_buffer_length %
-usb_maxpacket(urb->dev, urb->pipe,
-  usb_pipeout(urb->pipe))) == 0)) {
+   && maxp && (urb->transfer_buffer_length % maxp == 0)) {
/* need a 0-packet */
urb_priv->state = US_BULK0;
} else {
--
1.8.5.6