linux-kernel - Re: [PATCH] drivers/mmc/card/block.c: fix potential null dereference 'idata'

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Message-ID: <Pine.LNX.4.64.1105091631400.15483@pc-004.diku.dk>
Date:	Mon, 9 May 2011 16:32:41 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	Vladimir Motyka <vladimir.motyka@...il.com>
Cc:	cjb@...top.org, kernel-janitors@...r.kernel.org,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/mmc/card/block.c: fix potential null dereference
 'idata'

On Mon, 9 May 2011, Vladimir Motyka wrote:

> When allocation of idata fails there was a null dereferece.

Why not have a different label for the two cases?  That would make the 
code easier to statically analyze, and perhaps be more understandable as 
well.

julia


> Signed-off-by: Vladimir Motyka <vladimir.motyka@...il.com>
> 
> ---
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 407836d..3dec493 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -266,10 +266,10 @@ static struct mmc_blk_ioc_data
> *mmc_blk_ioctl_copy_from_user(
>  	return idata;
> 
>  copy_err:
> -	kfree(idata->buf);
> +	if(idata)
> +		kfree(idata->buf);
>  	kfree(idata);
>  	return ERR_PTR(err);
> -
>  }
> 
>  static int mmc_blk_ioctl_cmd(struct block_device *bdev,
> --
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