[PATCH] SOUND: usb/endpoint, fix dangling pointer use

[PATCH] SOUND: usb/endpoint, fix dangling pointer use

[Jiri Slaby]

Stanse found that in snd_usb_parse_audio_endpoints, there is a
dangling pointer dereference. When snd_usb_parse_audio_format fails,
fp is freed, and continue invoked. On the next loop, there is
"fp && fp->altsetting == 1 && fp->channels == 1" test, but fp is set
from the last iteration (but is bogus) and thus ilegally dereferenced.

Set fp to NULL before "continue".

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Daniel Mack <daniel@caiaq.de>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: Takashi Iwai <tiwai@suse.de>
---
 sound/usb/endpoint.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 9593b91..6f6596c 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -427,6 +427,7 @@ int snd_usb_parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
 		if (snd_usb_parse_audio_format(chip, fp, format, fmt, stream, alts) < 0) {
 			kfree(fp->rate_table);
 			kfree(fp);
+			fp = NULL;
 			continue;
 		}
 
-- 
1.7.1

Re: [PATCH] SOUND: usb/endpoint, fix dangling pointer use

[Daniel Mack]

On Mon, Jun 21, 2010 at 05:03:21PM +0200, Jiri Slaby wrote:
> Stanse found that in snd_usb_parse_audio_endpoints, there is a
> dangling pointer dereference. When snd_usb_parse_audio_format fails,
> fp is freed, and continue invoked. On the next loop, there is
> "fp && fp->altsetting == 1 && fp->channels == 1" test, but fp is set
> from the last iteration (but is bogus) and thus ilegally dereferenced.
> 
> Set fp to NULL before "continue".

Oh, absolutely. Thanks.

> Signed-off-by: Jiri Slaby <jslaby@suse.cz>

Acked-by: Daniel Mack <daniel@caiaq.de>

I think this should go thru the ALSA tree.


Daniel


> Cc: Clemens Ladisch <clemens@ladisch.de>
> Cc: Takashi Iwai <tiwai@suse.de>
> ---
>  sound/usb/endpoint.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
> index 9593b91..6f6596c 100644
> --- a/sound/usb/endpoint.c
> +++ b/sound/usb/endpoint.c
> @@ -427,6 +427,7 @@ int snd_usb_parse_audio_endpoints(struct snd_usb_audio *chip, int iface_no)
>  		if (snd_usb_parse_audio_format(chip, fp, format, fmt, stream, alts) < 0) {
>  			kfree(fp->rate_table);
>  			kfree(fp);
> +			fp = NULL;
>  			continue;
>  		}
>  
> -- 
> 1.7.1
> 
> 
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Re: [PATCH] SOUND: usb/endpoint, fix dangling pointer use

[Takashi Iwai]

At Mon, 21 Jun 2010 17:05:16 +0200,
Daniel Mack wrote:
> 
> On Mon, Jun 21, 2010 at 05:03:21PM +0200, Jiri Slaby wrote:
> > Stanse found that in snd_usb_parse_audio_endpoints, there is a
> > dangling pointer dereference. When snd_usb_parse_audio_format fails,
> > fp is freed, and continue invoked. On the next loop, there is
> > "fp && fp->altsetting == 1 && fp->channels == 1" test, but fp is set
> > from the last iteration (but is bogus) and thus ilegally dereferenced.
> > 
> > Set fp to NULL before "continue".
> 
> Oh, absolutely. Thanks.
> 
> > Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> 
> Acked-by: Daniel Mack <daniel@caiaq.de>
> 
> I think this should go thru the ALSA tree.

Yep, I applied it now.  Thanks!


Takashi