[PATCH] swsusp: Fix userland interface

["Rafael J. Wysocki" <rjw@sisk.pl>]

[2.6.22 candidate, IMHO]
---
From: Rafael J. Wysocki <rjw@sisk.pl>

Fix oops caused by 'cat /dev/snapshot', reported by Arkadiusz Miskiewicz, and
make it impossible to thaw tasks with the help of the swsusp userland interface
while there is a snapshot image ready to save.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 kernel/power/user.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Index: linux-2.6.22-rc4/kernel/power/user.c
===================================================================
--- linux-2.6.22-rc4.orig/kernel/power/user.c	2007-06-10 19:33:36.000000000 +0200
+++ linux-2.6.22-rc4/kernel/power/user.c	2007-06-10 19:35:59.000000000 +0200
@@ -99,6 +99,8 @@ static ssize_t snapshot_read(struct file
 	ssize_t res;
 
 	data = filp->private_data;
+	if (!data->ready)
+		return -ENODATA;
 	res = snapshot_read_next(&data->handle, count);
 	if (res > 0) {
 		if (copy_to_user(buf, data_of(data->handle), res))
@@ -163,7 +165,7 @@ static int snapshot_ioctl(struct inode *
 		break;
 
 	case SNAPSHOT_UNFREEZE:
-		if (!data->frozen)
+		if (!data->frozen || data->ready)
 			break;
 		mutex_lock(&pm_mutex);
 		thaw_processes();