PM: hibernate: Split off snapshot dev option

Make it possible to reduce the attack surface in case the snapshot
device is not to be used from userspace.

Signed-off-by: Domenico Andreoli <[email protected]>
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: cavokz

kernel/power/Kconfig

@@ -80,6 +80,18 @@ config HIBERNATION
 
 	  For more information take a look at <file:Documentation/power/swsusp.rst>.
 
+config HIBERNATION_SNAPSHOT_DEV
+	bool "Userspace snapshot device"
+	depends on HIBERNATION
+	default y
+	---help---
+	  Device used by the uswsusp tools.
+
+	  Say N if no snapshotting from userspace is needed, this also
+	  reduces the attack surface of the kernel.
+
+	  If in doubt, say Y.
+
 config PM_STD_PARTITION
 	string "Default resume partition"
 	depends on HIBERNATION

kernel/power/Makefile

@@ -10,7 +10,8 @@ obj-$(CONFIG_VT_CONSOLE_SLEEP)	+= console.o
 obj-$(CONFIG_FREEZER)		+= process.o
 obj-$(CONFIG_SUSPEND)		+= suspend.o
 obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
-obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o
+obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o
+obj-$(CONFIG_HIBERNATION_SNAPSHOT_DEV) += user.o
 obj-$(CONFIG_PM_AUTOSLEEP)	+= autosleep.o
 obj-$(CONFIG_PM_WAKELOCKS)	+= wakelock.o