2010-06-21 15:03:28

by Jiri Slaby

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

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 <[email protected]>
Cc: Daniel Mack <[email protected]>
Cc: Clemens Ladisch <[email protected]>
Cc: Takashi Iwai <[email protected]>
---
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

2010-06-21 15:05:22

by Daniel Mack

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

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 <[email protected]>

Acked-by: Daniel Mack <[email protected]>

I think this should go thru the ALSA tree.


Daniel


> Cc: Clemens Ladisch <[email protected]>
> Cc: Takashi Iwai <[email protected]>
> ---
> 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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2010-06-21 15:09:06

by Takashi Iwai

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

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 <[email protected]>
>
> Acked-by: Daniel Mack <[email protected]>
>
> I think this should go thru the ALSA tree.

Yep, I applied it now. Thanks!


Takashi