V4L/DVB (5400): 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.

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>

1 files changed, 3 insertions, 6 deletions

diff --git a/drivers/media/dvb/dvb-core/dvbdev.c b/drivers/media/dvb/dvb-core/dvbdev.c
index 490337b5ee3e..14a372a0fe8b 100644
--- a/drivers/media/dvb/dvb-core/dvbdev.c
+++ b/drivers/media/dvb/dvb-core/dvbdev.c
@@ -203,8 +203,7 @@ 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);
@@ -294,8 +293,7 @@ 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);
@@ -323,8 +321,7 @@ 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;