* [PATCH v2 1/2] hibernate: incorporate concurrency handling
2020-05-01 15:14 [PATCH v2 0/2] hibernate: add config option for snapshot device Domenico Andreoli
@ 2020-05-01 15:14 ` Domenico Andreoli
2020-05-01 15:14 ` [PATCH v2 2/2] hibernate: split snapshot dev option Domenico Andreoli
1 sibling, 0 replies; 3+ messages in thread
From: Domenico Andreoli @ 2020-05-01 15:14 UTC (permalink / raw)
To: Rafael J. Wysocki, Pavel Machek; +Cc: Linux PM, Domenico Andreoli
[-- Attachment #1: hibernate-incorporate-concurrency-handling --]
[-- Type: text/plain, Size: 4575 bytes --]
From: Domenico Andreoli <domenico.andreoli@linux.com>
Hibernation concurrency handling is currently delegated to user.c,
where it's also used for regulating the access to the snapshot device.
In the prospective of making user.c a separate configuration option,
such mutual exclusion is brought into hibernate.c and made available
through accessor helpers hereby introduced.
v2:
- move the mutual exclusion to hibernate.c (it was in user.c)
- switched to refcount_t API (it was atomic_t)
Signed-off-by: Domenico Andreoli <domenico.andreoli@linux.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Linux PM <linux-pm@vger.kernel.org>
---
kernel/power/hibernate.c | 20 ++++++++++++++++----
kernel/power/power.h | 4 ++--
kernel/power/user.c | 10 ++++------
3 files changed, 22 insertions(+), 12 deletions(-)
Index: b/kernel/power/user.c
===================================================================
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -37,8 +37,6 @@ static struct snapshot_data {
bool free_bitmaps;
} snapshot_state;
-atomic_t snapshot_device_available = ATOMIC_INIT(1);
-
static int snapshot_open(struct inode *inode, struct file *filp)
{
struct snapshot_data *data;
@@ -49,13 +47,13 @@ static int snapshot_open(struct inode *i
lock_system_sleep();
- if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
+ if (!hibernate_acquire()) {
error = -EBUSY;
goto Unlock;
}
if ((filp->f_flags & O_ACCMODE) == O_RDWR) {
- atomic_inc(&snapshot_device_available);
+ hibernate_release();
error = -ENOSYS;
goto Unlock;
}
@@ -92,7 +90,7 @@ static int snapshot_open(struct inode *i
__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
}
if (error)
- atomic_inc(&snapshot_device_available);
+ hibernate_release();
data->frozen = false;
data->ready = false;
@@ -122,7 +120,7 @@ static int snapshot_release(struct inode
}
pm_notifier_call_chain(data->mode == O_RDONLY ?
PM_POST_HIBERNATION : PM_POST_RESTORE);
- atomic_inc(&snapshot_device_available);
+ hibernate_release();
unlock_system_sleep();
Index: b/kernel/power/power.h
===================================================================
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -154,8 +154,8 @@ extern int snapshot_write_next(struct sn
extern void snapshot_write_finalize(struct snapshot_handle *handle);
extern int snapshot_image_loaded(struct snapshot_handle *handle);
-/* If unset, the snapshot device cannot be open. */
-extern atomic_t snapshot_device_available;
+extern bool hibernate_acquire(void);
+extern void hibernate_release(void);
extern sector_t alloc_swapdev_block(int swap);
extern void free_all_swap_pages(int swap);
Index: b/kernel/power/hibernate.c
===================================================================
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -67,6 +67,18 @@ bool freezer_test_done;
static const struct platform_hibernation_ops *hibernation_ops;
+static refcount_t hibernate_refcount = REFCOUNT_INIT(1);
+
+bool hibernate_acquire(void)
+{
+ return refcount_add_not_zero(-1, &hibernate_refcount);
+}
+
+void hibernate_release(void)
+{
+ refcount_inc(&hibernate_refcount);
+}
+
bool hibernation_available(void)
{
return nohibernate == 0 && !security_locked_down(LOCKDOWN_HIBERNATION);
@@ -704,7 +716,7 @@ int hibernate(void)
lock_system_sleep();
/* The snapshot device should not be opened while we're running */
- if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
+ if (!hibernate_acquire()) {
error = -EBUSY;
goto Unlock;
}
@@ -775,7 +787,7 @@ int hibernate(void)
Exit:
__pm_notifier_call_chain(PM_POST_HIBERNATION, nr_calls, NULL);
pm_restore_console();
- atomic_inc(&snapshot_device_available);
+ hibernate_release();
Unlock:
unlock_system_sleep();
pr_info("hibernation exit\n");
@@ -880,7 +892,7 @@ static int software_resume(void)
goto Unlock;
/* The snapshot device should not be opened while we're running */
- if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
+ if (!hibernate_acquire()) {
error = -EBUSY;
swsusp_close(FMODE_READ);
goto Unlock;
@@ -904,7 +916,7 @@ static int software_resume(void)
__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
pm_restore_console();
pr_info("resume failed (%d)\n", error);
- atomic_inc(&snapshot_device_available);
+ hibernate_release();
/* For success case, the suspend path will release the lock */
Unlock:
mutex_unlock(&system_transition_mutex);
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH v2 2/2] hibernate: split snapshot dev option
2020-05-01 15:14 [PATCH v2 0/2] hibernate: add config option for snapshot device Domenico Andreoli
2020-05-01 15:14 ` [PATCH v2 1/2] hibernate: incorporate concurrency handling Domenico Andreoli
@ 2020-05-01 15:14 ` Domenico Andreoli
1 sibling, 0 replies; 3+ messages in thread
From: Domenico Andreoli @ 2020-05-01 15:14 UTC (permalink / raw)
To: Rafael J. Wysocki, Pavel Machek; +Cc: Linux PM, Domenico Andreoli
[-- Attachment #1: hibernate-split-snapshot-dev-option --]
[-- Type: text/plain, Size: 2020 bytes --]
From: Domenico Andreoli <domenico.andreoli@linux.com>
Make it possible to reduce the attack surface in case the snapshot
device is not to be used from userspace.
v2:
- the option is enabled by default (it was disabled by default)
- remove the premature "DEPRECATED" marking
- drop the redefinition of mutual exclusion helpers (in v2 they are
owned by hibernte.c) in case the option is deselected
- add the help message to the config option
Signed-off-by: Domenico Andreoli <domenico.andreoli@linux.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Linux PM <linux-pm@vger.kernel.org>
---
kernel/power/Kconfig | 12 ++++++++++++
kernel/power/Makefile | 3 ++-
2 files changed, 14 insertions(+), 1 deletion(-)
Index: b/kernel/power/Kconfig
===================================================================
--- a/kernel/power/Kconfig
+++ b/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
Index: b/kernel/power/Makefile
===================================================================
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -10,7 +10,8 @@ obj-$(CONFIG_VT_CONSOLE_SLEEP) += consol
obj-$(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
^ permalink raw reply [flat|nested] 3+ messages in thread