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staging: comedi: use refcount while reading /proc/comedi 

In the seq_file 'show' handler for "/proc/comedi" - `comedi_read()` in
"comedi/proc.c",  call `comedi_dev_get_from_minor()` instead of
`comedi_dev_from_minor()` to increment the reference counter for the
`struct comedi_device` while it is being examined.  Call
`comedi_dev_put()` to decrement the reference afterwards.  Also acquire
the `attach_lock` rwsem while checking whether the device is attached.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2013-11-08 15:03:36 +00:00 committed by Greg Kroah-Hartman
parent a200fadca9
commit 616a3548e8
1 changed files with 5 additions and 1 deletions
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6
drivers/staging/comedi/proc.c
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@ -41,16 +41,20 @@ static int comedi_read(struct seq_file *m, void *v)
"driver_name, board_name, n_subdevices");
for (i = 0; i < COMEDI_NUM_BOARD_MINORS; i++) {
struct comedi_device *dev = comedi_dev_from_minor(i);
struct comedi_device *dev = comedi_dev_get_from_minor(i);
if (!dev)
continue;
down_read(&dev->attach_lock);
if (dev->attached) {
devices_q = 1;
seq_printf(m, "%2d: %-20s %-20s %4d\n",
i, dev->driver->driver_name,
dev->board_name, dev->n_subdevices);
}
up_read(&dev->attach_lock);
comedi_dev_put(dev);
}
if (!devices_q)
seq_puts(m, "no devices\n");