linux-kernel - Re: [PATCH] hda_hwdep: Fix possible buffer overflow

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Date:	Wed, 26 Oct 2011 14:58:43 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Alexander Stein <alexander.stein@...tec-electronic.com>
Cc:	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hda_hwdep: Fix possible buffer overflow

At Wed, 26 Oct 2011 09:48:12 +0200,
Alexander Stein wrote:
> 
> If a line in the firmware file is larger than the given buffer size (and
> so the firmware file size), size is set to a value larger than the actual
> buffer size. This results in an overflow in the buffer passed.
> Fix this by copying only up to 127 chars per line.

Actually this check should have been

	if (size > fw->size)
		size = fw->size;

Otherwise it doesn't make sense.
If the change is OK, could you resend the patch with it?


thanks,

Takashi

> Signed-off-by: Alexander Stein <alexander.stein@...tec-electronic.com>
> ---
>  sound/pci/hda/hda_hwdep.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/pci/hda/hda_hwdep.c b/sound/pci/hda/hda_hwdep.c
> index bf3ced5..61da08d 100644
> --- a/sound/pci/hda/hda_hwdep.c
> +++ b/sound/pci/hda/hda_hwdep.c
> @@ -745,6 +745,7 @@ static int parse_line_mode(char *buf, struct hda_bus *bus)
>   * if successfully copied a line
>   *
>   * the spaces at the beginning and the end of the line are stripped
> + * lines read are clamped to 127 chars
>   */
>  static int get_line_from_fw(char *buf, int size, struct firmware *fw)
>  {
> @@ -756,8 +757,6 @@ static int get_line_from_fw(char *buf, int size, struct firmware *fw)
>  	}
>  	if (!fw->size)
>  		return 0;
> -	if (size < fw->size)
> -		size = fw->size;
>  
>  	for (len = 0; len < fw->size; len++) {
>  		if (!*p)
> @@ -768,7 +767,8 @@ static int get_line_from_fw(char *buf, int size, struct firmware *fw)
>  			break;
>  		}
>  		if (len < size)
> -			*buf++ = *p++;
> +			*buf++ = *p;
> +		p++;
>  	}
>  	*buf = 0;
>  	fw->size -= len;
> -- 
> 1.7.3.4
> 
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