2015-12-29 18:50:53

by Insu Yun

Subject: [PATCH] cx231xx: correctly handling failed allocation

Since kmalloc can be failed in memory pressure,
if not properly handled, NULL dereference can be happend

Signed-off-by: Insu Yun <[email protected]>
---
drivers/media/usb/cx231xx/cx231xx-417.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/media/usb/cx231xx/cx231xx-417.c b/drivers/media/usb/cx231xx/cx231xx-417.c
index 47a98a2..9725e4f 100644
--- a/drivers/media/usb/cx231xx/cx231xx-417.c
+++ b/drivers/media/usb/cx231xx/cx231xx-417.c
@@ -1382,6 +1382,8 @@ static int cx231xx_bulk_copy(struct cx231xx *dev, struct urb *urb)
buffer_size = urb->actual_length;

buffer = kmalloc(buffer_size, GFP_ATOMIC);
+ if (!buffer)
+ return -ENOMEM;

memcpy(buffer, dma_q->ps_head, 3);
memcpy(buffer+3, p_buffer, buffer_size-3);
--
1.9.1

2015-12-29 19:05:44

by Devin Heitmueller

Subject: Re: [PATCH] cx231xx: correctly handling failed allocation

On Tue, Dec 29, 2015 at 1:53 PM, Insu Yun <[email protected]> wrote:
> Since kmalloc can be failed in memory pressure,
> if not properly handled, NULL dereference can be happend
>
> Signed-off-by: Insu Yun <[email protected]>
> ---
> drivers/media/usb/cx231xx/cx231xx-417.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/usb/cx231xx/cx231xx-417.c b/drivers/media/usb/cx231xx/cx231xx-417.c
> index 47a98a2..9725e4f 100644
> --- a/drivers/media/usb/cx231xx/cx231xx-417.c
> +++ b/drivers/media/usb/cx231xx/cx231xx-417.c
> @@ -1382,6 +1382,8 @@ static int cx231xx_bulk_copy(struct cx231xx *dev, struct urb *urb)
> buffer_size = urb->actual_length;
>
> buffer = kmalloc(buffer_size, GFP_ATOMIC);
> + if (!buffer)
> + return -ENOMEM;

A kmalloc() call inside a bulk handler running in softirq context?
That doesn't look right.

That said, I don't have any specific objection to the patch (which I'm
assuming came from some automated tool), but I suspect the cx231xx-417
code is probably completely broken. The only device I've ever seen
that has the cx23102 and cx23417 is one of the Polaris EVKs, which
AFAIK nobody has ever shipped a production design based on.

Devin

--
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com