Re: [Line6linux-devel] [PATCH] line6: Use kmemdup rather thanduplicating its implementation

From: Stefan Hajnoczi
Date: Mon Dec 03 2012 - 11:34:08 EST


On Mon, Dec 3, 2012 at 2:20 PM, Laurent Navet <laurent.navet@xxxxxxxxx> wrote:
> staging: line6: driver.c
> The semantic patch that makes this output is available
> in scripts/coccinelle/api/memdup.cocci.
>
> Signed-off-by: Laurent Navet <laurent.navet@xxxxxxxxx>
> ---
> drivers/staging/line6/driver.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/staging/line6/driver.c b/drivers/staging/line6/driver.c
> index f5c19b2..e1d6241 100644
> --- a/drivers/staging/line6/driver.c
> +++ b/drivers/staging/line6/driver.c
> @@ -331,14 +331,13 @@ int line6_version_request_async(struct usb_line6 *line6)
> char *buffer;
> int retval;
>
> - buffer = kmalloc(sizeof(line6_request_version), GFP_ATOMIC);
> + buffer = kmemdup(line6_request_version,
> + sizeof(line6_request_version), GFP_ATOMIC);
> if (buffer == NULL) {
> dev_err(line6->ifcdev, "Out of memory");
> return -ENOMEM;
> }
>
> - memcpy(buffer, line6_request_version, sizeof(line6_request_version));
> -
> retval = line6_send_raw_message_async(line6, buffer,
> sizeof(line6_request_version));
> kfree(buffer);
> --
> 1.7.10.4

Your change is fine but I'm not sure whether we should allocate memory
in the first place:

line6_send_raw_message_async() returns before the transfer is
complete. It submits one or more URBs but I cannot see a guarantee
that the buffer is no longer needed. It seems unsafe to kfree(buffer)
before the request is complete.

Since we already have const char line6_request_version[] we should
pass it directly without a temporary kmemdup() buffer.

Stefan
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