staging: comedi: fix result of memdup_user for user chanlist

If the channel list is not set in userspace we get an error at
PTR_ERR(async->cmd.chanlist). However, do_become_nonbusy(dev, s) cleans
up this pointer which causes a kernel ooops. Setting the channel list in
async to NULL and checking this in do_become_nonbusy prevents the oops.

[Ian Abbott] Also do the same for the chanlist allocated in
do_cmdtest_ioctl().

Signed-off-by: Bernd Porr <mail@berndporr.me.uk>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index fc3404882ae8d980aea01488e7b0c59bdacf3cf9..d7f63c483ad3c0721bc9f443827f8bcc2593a511 100644 (file)
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -1473,6 +1473,7 @@ static int do_cmd_ioctl(struct comedi_device *dev,
                                          async->cmd.chanlist_len * sizeof(int));
        if (IS_ERR(async->cmd.chanlist)) {
                ret = PTR_ERR(async->cmd.chanlist);
+               async->cmd.chanlist = NULL;
                dev_dbg(dev->class_dev, "memdup_user failed with code %d\n",
                        ret);
                goto cleanup;
@@ -1595,6 +1596,7 @@ static int do_cmdtest_ioctl(struct comedi_device *dev,
                                       cmd.chanlist_len * sizeof(int));
                if (IS_ERR(chanlist)) {
                        ret = PTR_ERR(chanlist);
+                       chanlist = NULL;
                        dev_dbg(dev->class_dev,
                                "memdup_user exited with code %d", ret);
                        goto cleanup;