[patch] ptp: oops in ptp_ioctl()

[Dan Carpenter]

If we pass ERR_PTR(-EFAULT) to kfree() then it's going to oops.

Fixes: 2ece068e1b1d ('ptp: use memdup_user().')
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 0b1ac6b..d637c93 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -211,6 +211,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, 
unsigned long arg)
                sysoff = memdup_user((void __user *)arg, sizeof(*sysoff));
                if (IS_ERR(sysoff)) {
                        err = PTR_ERR(sysoff);
+                       sysoff = NULL;
                        break;
                }
                if (sysoff->n_samples > PTP_MAX_SAMPLES) {