dvb-core: fix several locking related problems

dvb-core: fix several locking related problems

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.

(cherry picked from commit c278850206fd9df0bb62a72ca0b277fe20c5a452)

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>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/media/dvb/dvb-core/dmxdev.c b/drivers/media/dvb/dvb-core/dmxdev.c
index 988499dfddf8d8d17bcffbb6522231f9d1485fd0..ec473ebb327c5ae2f785a3ee303930019d2615ef 100644 (file)
--- a/drivers/media/dvb/dvb-core/dmxdev.c
+++ b/drivers/media/dvb/dvb-core/dmxdev.c
@@ -181,8 +181,7 @@ 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);
@@ -674,13 +673,8 @@ 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);

diff --git a/drivers/media/dvb/dvb-core/dvb_demux.c b/drivers/media/dvb/dvb-core/dvb_demux.c
index fcff5eab21a3fc050d5207f9538c99d6c6ee63bd..6d8d1c3df8631a4832b34954e44e5633cd3a34c6 100644 (file)
--- a/drivers/media/dvb/dvb-core/dvb_demux.c
+++ b/drivers/media/dvb/dvb-core/dvb_demux.c
@@ -673,8 +673,7 @@ static int dmx_ts_feed_stop_filtering(struct dmx_ts_feed *ts_feed)
        struct dvb_demux *demux = feed->demux;
        int ret;
 
-       if (mutex_lock_interruptible(&demux->mutex))
-               return -ERESTARTSYS;
+       mutex_lock(&demux->mutex);
 
        if (feed->state < DMX_STATE_GO) {
                mutex_unlock(&demux->mutex);
@@ -748,8 +747,7 @@ static int dvbdmx_release_ts_feed(struct dmx_demux *dmx,
        struct dvb_demux *demux = (struct dvb_demux *)dmx;
        struct dvb_demux_feed *feed = (struct dvb_demux_feed *)ts_feed;
 
-       if (mutex_lock_interruptible(&demux->mutex))
-               return -ERESTARTSYS;
+       mutex_lock(&demux->mutex);
 
        if (feed->state == DMX_STATE_FREE) {
                mutex_unlock(&demux->mutex);
@@ -916,8 +914,7 @@ static int dmx_section_feed_stop_filtering(struct dmx_section_feed *feed)
        struct dvb_demux *dvbdmx = dvbdmxfeed->demux;
        int ret;
 
-       if (mutex_lock_interruptible(&dvbdmx->mutex))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdmx->mutex);
 
        if (!dvbdmx->stop_feed) {
                mutex_unlock(&dvbdmx->mutex);
@@ -942,8 +939,7 @@ static int dmx_section_feed_release_filter(struct dmx_section_feed *feed,
        struct dvb_demux_feed *dvbdmxfeed = (struct dvb_demux_feed *)feed;
        struct dvb_demux *dvbdmx = dvbdmxfeed->demux;
 
-       if (mutex_lock_interruptible(&dvbdmx->mutex))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdmx->mutex);
 
        if (dvbdmxfilter->feed != dvbdmxfeed) {
                mutex_unlock(&dvbdmx->mutex);
@@ -1016,8 +1012,7 @@ static int dvbdmx_release_section_feed(struct dmx_demux *demux,
        struct dvb_demux_feed *dvbdmxfeed = (struct dvb_demux_feed *)feed;
        struct dvb_demux *dvbdmx = (struct dvb_demux *)demux;
 
-       if (mutex_lock_interruptible(&dvbdmx->mutex))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdmx->mutex);
 
        if (dvbdmxfeed->state == DMX_STATE_FREE) {
                mutex_unlock(&dvbdmx->mutex);
@@ -1126,8 +1121,7 @@ static int dvbdmx_connect_frontend(struct dmx_demux *demux,
        if (demux->frontend)
                return -EINVAL;
 
-       if (mutex_lock_interruptible(&dvbdemux->mutex))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdemux->mutex);
 
        demux->frontend = frontend;
        mutex_unlock(&dvbdemux->mutex);
@@ -1138,8 +1132,7 @@ static int dvbdmx_disconnect_frontend(struct dmx_demux *demux)
 {
        struct dvb_demux *dvbdemux = (struct dvb_demux *)demux;
 
-       if (mutex_lock_interruptible(&dvbdemux->mutex))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdemux->mutex);
 
        demux->frontend = NULL;
        mutex_unlock(&dvbdemux->mutex);

diff --git a/drivers/media/dvb/dvb-core/dvbdev.c b/drivers/media/dvb/dvb-core/dvbdev.c
index af35f3058d0f688a135a1fe20cb8b1fa9be0410e..b3a8cbbda62191e203ec257b7885f7ceb9f70ad6 100644 (file)
--- a/drivers/media/dvb/dvb-core/dvbdev.c
+++ b/drivers/media/dvb/dvb-core/dvbdev.c
@@ -204,8 +204,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
 
        int id;
 
-       if (mutex_lock_interruptible(&dvbdev_register_lock))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdev_register_lock);
 
        if ((id = dvbdev_get_free_id (adap, type)) < 0) {
                mutex_unlock(&dvbdev_register_lock);
@@ -295,8 +294,7 @@ int dvb_register_adapter(struct dvb_adapter *adap, const char *name, struct modu
 {
        int num;
 
-       if (mutex_lock_interruptible(&dvbdev_register_lock))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdev_register_lock);
 
        if ((num = dvbdev_get_free_adapter_num ()) < 0) {
                mutex_unlock(&dvbdev_register_lock);
@@ -324,8 +322,7 @@ EXPORT_SYMBOL(dvb_register_adapter);
 
 int dvb_unregister_adapter(struct dvb_adapter *adap)
 {
-       if (mutex_lock_interruptible(&dvbdev_register_lock))
-               return -ERESTARTSYS;
+       mutex_lock(&dvbdev_register_lock);
        list_del (&adap->list_head);
        mutex_unlock(&dvbdev_register_lock);
        return 0;