ALSA: bebob: potential info leak in hwdep_read()

commit b41c15f4e1c1f1657da15c482fa837c1b7384452 upstream.

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@oracle.com>
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201007074928.GA2529578@mwanda
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/sound/firewire/bebob/bebob_hwdep.c b/sound/firewire/bebob/bebob_hwdep.c
index 04c321e..a04b588 100644 (file)
--- a/sound/firewire/bebob/bebob_hwdep.c
+++ b/sound/firewire/bebob/bebob_hwdep.c
@@ -37,12 +37,11 @@ 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);