![Takashi Sakamoto](/assets/img/avatar_default.png)
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> Cc: stable@vger.kernel.org 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>
191 lines
4 KiB
C
191 lines
4 KiB
C
/*
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* tascam-hwdep.c - a part of driver for TASCAM FireWire series
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*
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* Copyright (c) 2015 Takashi Sakamoto
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*
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* Licensed under the terms of the GNU General Public License, version 2.
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*/
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/*
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* This codes give three functionality.
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*
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* 1.get firewire node information
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* 2.get notification about starting/stopping stream
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* 3.lock/unlock stream
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*/
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#include "tascam.h"
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static long hwdep_read(struct snd_hwdep *hwdep, char __user *buf, long count,
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loff_t *offset)
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{
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struct snd_tscm *tscm = hwdep->private_data;
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DEFINE_WAIT(wait);
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union snd_firewire_event event = {
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.lock_status.type = SNDRV_FIREWIRE_EVENT_LOCK_STATUS,
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};
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spin_lock_irq(&tscm->lock);
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while (!tscm->dev_lock_changed) {
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prepare_to_wait(&tscm->hwdep_wait, &wait, TASK_INTERRUPTIBLE);
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spin_unlock_irq(&tscm->lock);
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schedule();
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finish_wait(&tscm->hwdep_wait, &wait);
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if (signal_pending(current))
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return -ERESTARTSYS;
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spin_lock_irq(&tscm->lock);
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}
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event.lock_status.status = (tscm->dev_lock_count > 0);
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tscm->dev_lock_changed = false;
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spin_unlock_irq(&tscm->lock);
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count = min_t(long, count, sizeof(event.lock_status));
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if (copy_to_user(buf, &event, count))
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return -EFAULT;
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return count;
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}
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static unsigned int hwdep_poll(struct snd_hwdep *hwdep, struct file *file,
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poll_table *wait)
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{
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struct snd_tscm *tscm = hwdep->private_data;
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unsigned int events;
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poll_wait(file, &tscm->hwdep_wait, wait);
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spin_lock_irq(&tscm->lock);
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if (tscm->dev_lock_changed)
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events = POLLIN | POLLRDNORM;
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else
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events = 0;
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spin_unlock_irq(&tscm->lock);
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return events;
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}
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static int hwdep_get_info(struct snd_tscm *tscm, void __user *arg)
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{
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struct fw_device *dev = fw_parent_device(tscm->unit);
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struct snd_firewire_get_info info;
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memset(&info, 0, sizeof(info));
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info.type = SNDRV_FIREWIRE_TYPE_TASCAM;
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info.card = dev->card->index;
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*(__be32 *)&info.guid[0] = cpu_to_be32(dev->config_rom[3]);
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*(__be32 *)&info.guid[4] = cpu_to_be32(dev->config_rom[4]);
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strlcpy(info.device_name, dev_name(&dev->device),
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sizeof(info.device_name));
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if (copy_to_user(arg, &info, sizeof(info)))
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return -EFAULT;
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return 0;
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}
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static int hwdep_lock(struct snd_tscm *tscm)
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{
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int err;
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spin_lock_irq(&tscm->lock);
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if (tscm->dev_lock_count == 0) {
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tscm->dev_lock_count = -1;
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err = 0;
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} else {
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err = -EBUSY;
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}
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spin_unlock_irq(&tscm->lock);
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return err;
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}
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static int hwdep_unlock(struct snd_tscm *tscm)
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{
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int err;
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spin_lock_irq(&tscm->lock);
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if (tscm->dev_lock_count == -1) {
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tscm->dev_lock_count = 0;
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err = 0;
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} else {
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err = -EBADFD;
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}
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spin_unlock_irq(&tscm->lock);
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return err;
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}
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static int hwdep_release(struct snd_hwdep *hwdep, struct file *file)
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{
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struct snd_tscm *tscm = hwdep->private_data;
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spin_lock_irq(&tscm->lock);
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if (tscm->dev_lock_count == -1)
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tscm->dev_lock_count = 0;
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spin_unlock_irq(&tscm->lock);
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return 0;
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}
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static int hwdep_ioctl(struct snd_hwdep *hwdep, struct file *file,
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unsigned int cmd, unsigned long arg)
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{
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struct snd_tscm *tscm = hwdep->private_data;
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switch (cmd) {
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case SNDRV_FIREWIRE_IOCTL_GET_INFO:
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return hwdep_get_info(tscm, (void __user *)arg);
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case SNDRV_FIREWIRE_IOCTL_LOCK:
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return hwdep_lock(tscm);
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case SNDRV_FIREWIRE_IOCTL_UNLOCK:
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return hwdep_unlock(tscm);
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default:
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return -ENOIOCTLCMD;
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}
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}
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#ifdef CONFIG_COMPAT
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static int hwdep_compat_ioctl(struct snd_hwdep *hwdep, struct file *file,
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unsigned int cmd, unsigned long arg)
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{
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return hwdep_ioctl(hwdep, file, cmd,
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(unsigned long)compat_ptr(arg));
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}
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#else
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#define hwdep_compat_ioctl NULL
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#endif
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static const struct snd_hwdep_ops hwdep_ops = {
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.read = hwdep_read,
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.release = hwdep_release,
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.poll = hwdep_poll,
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.ioctl = hwdep_ioctl,
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.ioctl_compat = hwdep_compat_ioctl,
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};
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int snd_tscm_create_hwdep_device(struct snd_tscm *tscm)
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{
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struct snd_hwdep *hwdep;
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int err;
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err = snd_hwdep_new(tscm->card, "Tascam", 0, &hwdep);
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if (err < 0)
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return err;
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strcpy(hwdep->name, "Tascam");
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hwdep->iface = SNDRV_HWDEP_IFACE_FW_TASCAM;
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hwdep->ops = hwdep_ops;
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hwdep->private_data = tscm;
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hwdep->exclusive = true;
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return err;
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}
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