linux-kernel - [PATCH] pps: locking scheme fix up for PPS

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Date:	Fri,  6 Nov 2009 11:49:55 +0100
From:	Rodolfo Giometti <giometti@...ux.it>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rodolfo Giometti <giometti@...ux.it>
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@...ux.it>
Tested-by: Reg Clemens <clemens@....com>
---
 drivers/pps/pps.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index fea17e7..ca5183b 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;
 
-- 
1.6.3.3

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