diff options
| author | Federico Vaga <federico.vaga@gmail.com> | 2011-10-29 09:45:39 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-12-09 08:52:40 -0800 |
| commit | 261dbf437bce1d339c358e6566925905e49c13fe (patch) | |
| tree | 0550c193a8ad97b70d58d6a87f953033fe3a7ab7 | |
| parent | 9649803f2de0d2e77bdd7c5e1cbd4a7b3833f1e8 (diff) | |
Staging: comedi: fix mmap_count
commit df30b21cb0eed5ba8a8e0cdfeebc66ba8cde821d upstream.
In comedi_fops, mmap_count is decremented at comedi_vm_ops->close but
it is not incremented at comedi_vm_ops->open. This may result in a negative
counter. The patch introduces the open method to keep the counter
consistent.
The bug was triggerd by this sample code:
mmap(0, ...., comedi_fd);
fork();
exit(0);
Acked-by: Alessandro Rubini <rubini@gnudd.com>
Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | drivers/staging/comedi/comedi_fops.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 2cbb17945c5..69bd6f01bf6 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -1432,7 +1432,21 @@ static int do_cancel(struct comedi_device *dev, struct comedi_subdevice *s) return ret; } -static void comedi_unmap(struct vm_area_struct *area) + +static void comedi_vm_open(struct vm_area_struct *area) +{ + struct comedi_async *async; + struct comedi_device *dev; + + async = area->vm_private_data; + dev = async->subdevice->device; + + mutex_lock(&dev->mutex); + async->mmap_count++; + mutex_unlock(&dev->mutex); +} + +static void comedi_vm_close(struct vm_area_struct *area) { struct comedi_async *async; struct comedi_device *dev; @@ -1446,7 +1460,8 @@ static void comedi_unmap(struct vm_area_struct *area) } static struct vm_operations_struct comedi_vm_ops = { - .close = comedi_unmap, + .open = comedi_vm_open, + .close = comedi_vm_close, }; static int comedi_mmap(struct file *file, struct vm_area_struct *vma) |