linux-kernel - Re: [PATCH] Staging: dgnc: check kzalloc result

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Message-ID: <20150309112412.GC10964@mwanda>
Date:	Mon, 9 Mar 2015 14:24:12 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Matteo Semenzato <mattew8898@...il.com>
Cc:	gregkh@...uxfoundation.org, lidza.louina@...il.com,
	markh@...pro.net, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: dgnc: check kzalloc result

On Sun, Mar 08, 2015 at 05:54:07PM +0100, Matteo Semenzato wrote:
> From: Matteo Semenzato <mattew8898@...il.com>
> 
> Return -ENOMEM if allocating brd->flipbuf fails.
> 
> Signed-off-by: Matteo Semenzato <mattew8898@...il.com>
> ---
>  drivers/staging/dgnc/dgnc_driver.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/staging/dgnc/dgnc_driver.c b/drivers/staging/dgnc/dgnc_driver.c
> index f177d3a..711af02 100644
> --- a/drivers/staging/dgnc/dgnc_driver.c
> +++ b/drivers/staging/dgnc/dgnc_driver.c
> @@ -622,6 +622,10 @@ static int dgnc_found_board(struct pci_dev *pdev, int id)
>  	 * context, and there are no locks held.
>  	 */
>  	brd->flipbuf = kzalloc(MYFLIPLEN, GFP_KERNEL);
> +	if (!brd->flipbuf) {
> +		kfree(brd);
> +		return -ENOMEM;

This leaves a freed pointer in "dgnc_Board[dgnc_NumBoards]" which is
sort of ugly.  It doesn't free "brd->msgbuf_head" which is a bug.

Please read my essay on error hanling:
https://plus.google.com/106378716002406849458

What we want is :

	ret = do_one();
	if (ret)
		return ret;
	ret = do_two();
	if (ret)
		goto undo_one;

	ret = do_three();
	if (ret)
		goto undo_two;

	return 0;

err_undo_two:
	undo_two();
err_undo_one:
	undo_one();

	return ret;

Basically, a list of commands and a mirror list of undos.  This is
standard kernel style and the error handling basically writes itself
automatically.

regards,
dan carpenter

> +	}
>  
>  	wake_up_interruptible(&brd->state_wait);
>  
> -- 
> 2.3.1
> 
> _______________________________________________
> devel mailing list
> devel@...uxdriverproject.org
> http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
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