On Wed, 18 Jul 2018 17:07:00 +0200,
Srikanth K H wrote:
>
> If the timer object is created without the card for entries
> "SNDRV_TIMER_CLASS_CARD" and "SNDRV_TIMER_CLASS_PCM", then
> while reading the sound info entry in function
> "snd_timer_proc_read" the card information is directly
> dereferenced without checking for NULL and hence kernel
> panic occur. So as preventive measure while the creating
> the sound timer object is created the card information
> availability is checked for the mentioned entries and
> returned error if its NULL.
>
> Signed-off-by: Srikanth K H <srikanth.h@xxxxxxxxxxx>
> ---
> sound/core/timer.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/sound/core/timer.c b/sound/core/timer.c
> index c7be4f1..06f734f 100644
> --- a/sound/core/timer.c
> +++ b/sound/core/timer.c
> @@ -883,6 +883,11 @@ int snd_timer_new(struct snd_card *card, char *id, struct snd_timer_id *tid,
>
> if (snd_BUG_ON(!tid))
> return -EINVAL;
> + if (tid->dev_class == SNDRV_TIMER_CLASS_CARD ||
> + tid->dev_class == SNDRV_TIMER_CLASS_PCM) {
> + if (WARN_ON(!card))
> + return -EINVAL;
> + }
> if (rtimer)
> *rtimer = NULL;
> timer = kzalloc(sizeof(*timer), GFP_KERNEL);
> @@ -1192,12 +1197,10 @@ static void snd_timer_proc_read(struct snd_info_entry *entry,
> break;
> case SNDRV_TIMER_CLASS_CARD:
> snd_iprintf(buffer, "C%i-%i: ",
> - timer->card ? timer->card->number : -1,
> - timer->tmr_device);
> + timer->card->number, timer->tmr_device);
> break;
> case SNDRV_TIMER_CLASS_PCM:
> - snd_iprintf(buffer, "P%i-%i-%i: ",
> - timer->card ? timer->card->number : -1,
> + snd_iprintf(buffer, "P%i-%i-%i: ", timer->card->number,
> timer->tmr_device, timer->tmr_subdevice);
> break;
The checks in proc are moot if we guarantee the non-NULL card at
snd_timer_new() in the above.
So it's not about fixing in sound module. It serves right. Your
patch would add a sanity check to catch a buggy code in the caller
side.
thanks,
Takashi
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