pps: locking scheme fix up for PPS_GETPARAMS

Userland programs may read/write PPS parameters at same time and these
operations may corrupt PPS data.

Signed-off-by: Rodolfo Giometti <giometti@linux.it>
Tested-by: Reg Clemens <clemens@dwf.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index fea17e7805e9..ca5183bdad85 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -71,9 +71,14 @@ static long pps_cdev_ioctl(struct file *file,
         case PPS_GETPARAMS:
                 pr_debug("PPS_GETPARAMS: source %d\n", pps->id);
 
-                /* Return current parameters */
-                err = copy_to_user(uarg, &pps->params,
-                                                sizeof(struct pps_kparams));
+                spin_lock_irq(&pps->lock);
+
+                /* Get the current parameters */
+                params = pps->params;
+
+                spin_unlock_irq(&pps->lock);
+
+                err = copy_to_user(uarg, &params, sizeof(struct pps_kparams));
                 if (err)
                         return -EFAULT;