linux-kernel - Re: [PATCH 3/8] firewire: cdev: reduce stack usage by ioctl

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Message-ID: <tkrat.ec38f27900b7af20@s5r6.in-berlin.de>
Date:	Wed, 14 Oct 2009 22:43:54 +0200 (CEST)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] firewire: cdev: reduce stack usage by ioctl_dispatch

I wrote:
> --- linux-2.6.31.orig/drivers/firewire/core-cdev.c
> +++ linux-2.6.31/drivers/firewire/core-cdev.c
> @@ -1299,28 +1299,47 @@ static int (* const ioctl_handlers[])(st
>  static int dispatch_ioctl(struct client *client,
>  			  unsigned int cmd, void __user *arg)
>  {
> -	char buffer[256];
> +	char buffer[40];
>  	int ret;
>  
> +#define check_ioctl_size(x) BUILD_BUG_ON(_IOC_SIZE(x) > sizeof(buffer))
> +
> +	check_ioctl_size(FW_CDEV_IOC_GET_INFO);
> +	check_ioctl_size(FW_CDEV_IOC_SEND_REQUEST);
[...]

With linux 2.6.32-rc1's version of BUILD_BUG_ON, this adds sparse
warnings (seen with sparse 0.4.2):

drivers/firewire/core-cdev.c:1308:9: error: bad integer constant expression
drivers/firewire/core-cdev.c:1309:9: error: bad integer constant expression
[...]

Back to the drawing board.
-- 
Stefan Richter
-=====-==--= =-=- -===-
http://arcgraph.de/sr/

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