[PATCH -mm] swsusp: Fix possible oops in userland interface

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

The SNAPSHOT_PMOPS and SNAPSHOT_S2RAM ioctls can Oops if they are called from
a kernel that doesn't set pm_ops (eg. non-ACPI kernel on a PC).  Fix it.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
---
 kernel/power/user.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Index: linux-2.6.20-rc6-mm3/kernel/power/user.c
===================================================================
--- linux-2.6.20-rc6-mm3.orig/kernel/power/user.c	2007-02-04 18:36:21.000000000 +0100
+++ linux-2.6.20-rc6-mm3/kernel/power/user.c	2007-02-04 18:56:53.000000000 +0100
@@ -341,6 +341,11 @@ static int snapshot_ioctl(struct inode *
 		break;
 
 	case SNAPSHOT_S2RAM:
+		if (!pm_ops) {
+			error = -ENOSYS;
+			break;
+		}
+
 		if (!data->frozen) {
 			error = -EPERM;
 			break;
@@ -383,8 +388,12 @@ static int snapshot_ioctl(struct inode *
 		switch (arg) {
 
 		case PMOPS_PREPARE:
-			data->platform_suspend = 1;
-			error = 0;
+			if (pm_ops && pm_ops->enter) {
+				data->platform_suspend = 1;
+				error = 0;
+			} else {
+				error = -ENOSYS;
+			}
 			break;
 
 		case PMOPS_ENTER:
-
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