linux-kernel - Re: [PATCH v2] sound/oss: remove offset from load

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Message-ID: <s5hhbauc4zs.wl%tiwai@suse.de>
Date:	Wed, 23 Mar 2011 14:59:19 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Dan Rosenberg <drosenberg@...curity.com>
Cc:	perex@...ex.cz, alsa-devel@...a-project.org, security@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sound/oss: remove offset from load_patch callbacks

At Wed, 23 Mar 2011 09:47:22 -0400,
Dan Rosenberg wrote:
> --- a/sound/oss/midi_synth.c
> +++ b/sound/oss/midi_synth.c
> @@ -508,16 +506,15 @@ midi_synth_load_patch(int dev, int format, const char __user *addr,
>  	 * been transferred already.
>  	 */
>  
> -	if(copy_from_user(&((char *) &sysex)[offs], &(addr)[offs], hdr_size - offs))
> +	if (copy_from_user(&sysex, addr, hdr_size))

Please correct the comment in the above as well.
With this change, the transfer is no longer partial.

> --- a/sound/oss/opl3.c
> +++ b/sound/oss/opl3.c
...
> @@ -834,7 +834,7 @@ static int opl3_load_patch(int dev, int format, const char __user *addr,
>  	 * What the fuck is going on here?  We leave junk in the beginning
>  	 * of ins and then check the field pretty close to that beginning?
>  	 */
> -	if(copy_from_user(&((char *) &ins)[offs], addr + offs, sizeof(ins) - offs))
> +	if (copy_from_user(&ins, addr, sizeof(ins)))

Ditto.

>  		return -EFAULT;
>  
>  	if (ins.channel < 0 || ins.channel >= SBFM_MAXINSTR)
> diff --git a/sound/oss/sequencer.c b/sound/oss/sequencer.c
> index 5ea1098..2e842cb 100644
> --- a/sound/oss/sequencer.c
> +++ b/sound/oss/sequencer.c
> @@ -241,7 +241,7 @@ int sequencer_write(int dev, struct file *file, const char __user *buf, int coun
>  				return -ENXIO;
>  
>  			fmt = (*(short *) &event_rec[0]) & 0xffff;
> -			err = synth_devs[dev]->load_patch(dev, fmt, buf, p + 4, c, 0);
> +			err = synth_devs[dev]->load_patch(dev, fmt, buf, c, 0);

The address must be "buf + p + 4" instead of "buf", when you omit the
offset argument.


thanks,

Takashi
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