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authorTakashi Sakamoto <o-takashi@sakamocchi.jp>2016-08-31 20:15:32 +0900
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-09-15 08:27:53 +0200
commitad3bccfd7d6c0d9b263977492f2f712f1859b5b2 (patch)
treeee362f7a0ce929dfc43aa5c6d9ced1bf8fca0286
parent9947ec2c04d30412a06e45a4af03f28c2d76d1f6 (diff)
ALSA: firewire-tascam: accessing to user space outside spinlock
commit 04b2d9c9c319277ad4fbbb71855c256a9f4d5f98 upstream. In hwdep interface of firewire-tascam driver, accessing to user space is in a critical section with disabled local interrupt. Depending on architecture, accessing to user space can cause page fault exception. Then local processor stores machine status and handle the synchronous event. A handler corresponding to the event can call task scheduler to wait for preparing pages. In a case of usage of single core processor, the state to disable local interrupt is worse because it doesn't handle usual interrupts from hardware. This commit fixes this bug, by performing the accessing outside spinlock. Reported-by: Vaishali Thakkar <vaishali.thakkar@oracle.com> Fixes: e5e0c3dd257b('ALSA: firewire-tascam: add hwdep interface') Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--sound/firewire/tascam/tascam-hwdep.c33
1 files changed, 11 insertions, 22 deletions
diff --git a/sound/firewire/tascam/tascam-hwdep.c b/sound/firewire/tascam/tascam-hwdep.c
index 131267c3a042..106406cbfaa3 100644
--- a/sound/firewire/tascam/tascam-hwdep.c
+++ b/sound/firewire/tascam/tascam-hwdep.c
@@ -16,31 +16,14 @@
#include "tascam.h"
-static long hwdep_read_locked(struct snd_tscm *tscm, char __user *buf,
- long count)
-{
- union snd_firewire_event event;
-
- memset(&event, 0, sizeof(event));
-
- event.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS;
- event.lock_status.status = (tscm->dev_lock_count > 0);
- tscm->dev_lock_changed = false;
-
- count = min_t(long, count, sizeof(event.lock_status));
-
- if (copy_to_user(buf, &event, count))
- return -EFAULT;
-
- return count;
-}
-
static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
loff_t *offset)
{
struct snd_tscm *tscm = hwdep->private_data;
DEFINE_WAIT(wait);
- union snd_firewire_event event;
+ union snd_firewire_event event = {
+ .lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS,
+ };
spin_lock_irq(&tscm->lock);
@@ -54,10 +37,16 @@ static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
spin_lock_irq(&tscm->lock);
}
- memset(&event, 0, sizeof(event));
- count = hwdep_read_locked(tscm, buf, count);
+ event.lock_status.status = (tscm->dev_lock_count > 0);
+ tscm->dev_lock_changed = false;
+
spin_unlock_irq(&tscm->lock);
+ count = min_t(long, count, sizeof(event.lock_status));
+
+ if (copy_to_user(buf, &event, count))
+ return -EFAULT;
+
return count;
}