Hi,
Thanks for the patch.
On Wed, Oct 07, 2020 at 10:49:28AM +0300, Dan Carpenter wrote:
> The "count" variable needs to be capped on every path so that we don't
> copy too much information to the user.
>
> Fixes: 618eabeae711 ("ALSA: bebob: Add hwdep interface")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> sound/firewire/bebob/bebob_hwdep.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/sound/firewire/bebob/bebob_hwdep.c b/sound/firewire/bebob/bebob_hwdep.c
> index 45b740f44c45..c362eb38ab90 100644
> --- a/sound/firewire/bebob/bebob_hwdep.c
> +++ b/sound/firewire/bebob/bebob_hwdep.c
> @@ -36,12 +36,11 @@ hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
> }
>
> memset(&event, 0, sizeof(event));
> + count = min_t(long, count, sizeof(event.lock_status));
> if (bebob->dev_lock_changed) {
> event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
> event.lock_status.status = (bebob->dev_lock_count > 0);
> bebob->dev_lock_changed = false;
> -
> - count = min_t(long, count, sizeof(event.lock_status));
> }
>
> spin_unlock_irq(&bebob->lock);
> --
> 2.28.0
Indeed, the bug can leak the contents of kernel memory into user space
unintentionally for the size indicated by ALSA HwDep application...
I will check the other drivers in ALSA firewire stack later for safe.
Thanks
Takashi Sakamoto
