Messages in this thread Patch in this message | | | Date | Thu, 30 Apr 2009 13:18:18 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] dvb-core: Fix potential mutex_unlock without mutex_lock in dvb_dvr_read |
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On Thu, 23 Apr 2009 18:32:13 +0100 Simon Arlott <simon@fire.lp0.eu> wrote:
> dvb_dvr_read may unlock the dmxdev mutex and return -ENODEV, > except this function is a file op and will never be called > with the mutex held. > > There's existing mutex_lock and mutex_unlock around the actual > read but it's commented out. These should probably be uncommented > but the read blocks and this could block another non-blocking > reader on the mutex instead. > > This change comments out the extra mutex_unlock. > > Signed-off-by: Simon Arlott <simon@fire.lp0.eu> > --- > This has been on my TODO list for far too long... I did come > up with a mutex_trylock/mutex_lock_interruptible version but > claiming that it'll block when it may not doesn't make sense > (and any blocking read would cause all non-blocking reads to > continually return -EWOULDBLOCK until there is data). > > drivers/media/dvb/dvb-core/dmxdev.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/media/dvb/dvb-core/dmxdev.c b/drivers/media/dvb/dvb-core/dmxdev.c > index c35fbb8..d6d098a 100644 > --- a/drivers/media/dvb/dvb-core/dmxdev.c > +++ b/drivers/media/dvb/dvb-core/dmxdev.c > @@ -247,7 +247,7 @@ static ssize_t dvb_dvr_read(struct file *file, char __user *buf, size_t count, > int ret; > > if (dmxdev->exit) { > - mutex_unlock(&dmxdev->mutex); > + //mutex_unlock(&dmxdev->mutex); > return -ENODEV; > }
Is there any value in retaining all the commented-out lock operations, or can we zap 'em?
--- a/drivers/media/dvb/dvb-core/dmxdev.c~dvb-core-fix-potential-mutex_unlock-without-mutex_lock-in-dvb_dvr_read-fix +++ a/drivers/media/dvb/dvb-core/dmxdev.c @@ -244,19 +244,13 @@ static ssize_t dvb_dvr_read(struct file { struct dvb_device *dvbdev = file->private_data; struct dmxdev *dmxdev = dvbdev->priv; - int ret; - if (dmxdev->exit) { - //mutex_unlock(&dmxdev->mutex); + if (dmxdev->exit) return -ENODEV; - } - //mutex_lock(&dmxdev->mutex); - ret = dvb_dmxdev_buffer_read(&dmxdev->dvr_buffer, - file->f_flags & O_NONBLOCK, - buf, count, ppos); - //mutex_unlock(&dmxdev->mutex); - return ret; + return dvb_dmxdev_buffer_read(&dmxdev->dvr_buffer, + file->f_flags & O_NONBLOCK, + buf, count, ppos); } static int dvb_dvr_set_buffer_size(struct dmxdev *dmxdev, _
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