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V4L/DVB (5400): Core: fix several locking related problems

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Fix several instances of dvb-core functions using mutex_lock_interruptible
and returning -ERESTARTSYS where the calling function will either never
retry or never check the return value.
These cause a race condition with dvb_dmxdev_filter_free and
dvb_dvr_release, both of which are filesystem release functions whose
return value is ignored and will never be retried.  When this happens it
becomes impossible to open dvr0 again (-EBUSY) since it has not been
released properly.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-By: Johannes Stezenbach <js@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
This commit is contained in:
Simon Arlott
2007-03-10 06:21:25 -03:00
committed by Mauro Carvalho Chehab
parent b10fece583
commit c278850206
3 changed files with 13 additions and 29 deletions
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12
drivers/media/dvb/dvb-core/dmxdev.c
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@@ -180,8 +180,7 @@ static int dvb_dvr_release(struct inode *inode, struct file *file)
struct dvb_device *dvbdev = file->private_data;
struct dmxdev *dmxdev = dvbdev->priv;
if (mutex_lock_interruptible(&dmxdev->mutex))
return -ERESTARTSYS;
mutex_lock(&dmxdev->mutex);
if ((file->f_flags & O_ACCMODE) == O_WRONLY) {
dmxdev->demux->disconnect_frontend(dmxdev->demux);
@@ -673,13 +672,8 @@ static int dvb_demux_open(struct inode *inode, struct file *file)
static int dvb_dmxdev_filter_free(struct dmxdev *dmxdev,
struct dmxdev_filter *dmxdevfilter)
{
if (mutex_lock_interruptible(&dmxdev->mutex))
return -ERESTARTSYS;
if (mutex_lock_interruptible(&dmxdevfilter->mutex)) {
mutex_unlock(&dmxdev->mutex);
return -ERESTARTSYS;
}
mutex_lock(&dmxdev->mutex);
mutex_lock(&dmxdevfilter->mutex);
dvb_dmxdev_filter_stop(dmxdevfilter);
dvb_dmxdev_filter_reset(dmxdevfilter);