pps: locking scheme fix up for PPS_GETPARAMS
Rodolfo Giometti [Wed, 11 Nov 2009 22:26:52 +0000 (14:26 -0800)]
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

index fea17e7..ca5183b 100644 (file)
@@ -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;