linux-kernel - Re: [PATCH] usbip: usbip_host_common: Use struct

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Message-ID: <c5315c1f-5329-3f7b-0b70-a2337671320c@embeddedor.com>
Date:   Thu, 23 May 2019 09:52:08 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Valentina Manea <valentina.manea.m@...il.com>,
        Shuah Khan <shuah@...nel.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usbip: usbip_host_common: Use struct_size() in realloc()

Hi all,

Sorry, please, drop this patch.

Thanks
--
Gustavo

On 5/23/19 9:40 AM, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct foo {
>     int stuff;
>     struct boo entry[];
> };
> 
> size = sizeof(struct foo) + count * sizeof(struct boo);
> instance = realloc(instance, size);
> 
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
> 
> size = struct_size(instance, entry, count);
> 
> or
> 
> instance = realloc(instance, struct_size(instance, entry, count));
> 
> Notice that, in this case, variable size is not necessary,
> hence it is removed.
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
> 
> Notice that checkpatch reports the following warning:
> 
> WARNING: line over 80 characters
> #57: FILE: tools/usb/usbip/libsrc/usbip_host_common.c:90:
> +	edev = realloc(edev, struct_size(edev, uinf, edev->udev.bNumInterfaces));
> 
> The line above is 81-character long. So, I think we should be fine
> with that, instead of split it into two lines like:
> 
> edev = realloc(edev,
> 	       struct_size(edev, uinf, edev->udev.bNumInterfaces));
> 
> Thanks
> --
> Gustavo
> 
>  tools/usb/usbip/libsrc/usbip_host_common.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/tools/usb/usbip/libsrc/usbip_host_common.c b/tools/usb/usbip/libsrc/usbip_host_common.c
> index 2813aa821c82..1645d02a52af 100644
> --- a/tools/usb/usbip/libsrc/usbip_host_common.c
> +++ b/tools/usb/usbip/libsrc/usbip_host_common.c
> @@ -67,7 +67,6 @@ struct usbip_exported_device *usbip_exported_device_new(
>  {
>  	struct usbip_exported_device *edev = NULL;
>  	struct usbip_exported_device *edev_old;
> -	size_t size;
>  	int i;
>  
>  	edev = calloc(1, sizeof(struct usbip_exported_device));
> @@ -87,11 +86,8 @@ struct usbip_exported_device *usbip_exported_device_new(
>  		goto err;
>  
>  	/* reallocate buffer to include usb interface data */
> -	size = sizeof(struct usbip_exported_device) +
> -		edev->udev.bNumInterfaces * sizeof(struct usbip_usb_interface);
> -
>  	edev_old = edev;
> -	edev = realloc(edev, size);
> +	edev = realloc(edev, struct_size(edev, uinf, edev->udev.bNumInterfaces));
>  	if (!edev) {
>  		edev = edev_old;
>  		dbg("realloc failed");
>