From cbf83cc5a29dba480cf1ba1c5e3417a0d4a31410 Mon Sep 17 00:00:00 2001
From: Rodolfo Giometti <giometti@linux.it>
Date: Wed, 11 Nov 2009 14:26:52 -0800
Subject: [PATCH] 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>
---
 drivers/pps/pps.c | 11 ++++++++---
 1 file 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;