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Subject[PATCH 3.12 098/212] PM / Hibernate: Do not crash kernel in free_basic_memory_bitmaps()
3.12-stable review patch.  If anyone has any objections, please let me know.


From: "Rafael J. Wysocki" <>

commit 6a0c7cd33075f6b7f1d80145bb19812beb3fc5c9 upstream.

I have received a report about the BUG_ON() in free_basic_memory_bitmaps()
triggering mysteriously during an aborted s2disk hibernation attempt.
The only way I can explain that is that /dev/snapshot was first
opened for writing (resume mode), then closed and then opened again
for reading and closed again without freezing tasks. In that case
the first invocation of snapshot_open() would set the free_bitmaps
flag in snapshot_state, which is a static variable. That flag
wouldn't be cleared later and the second invocation of snapshot_open()
would just leave it like that, so the subsequent snapshot_release()
would see data->frozen set and free_basic_memory_bitmaps() would be
called unnecessarily.

To prevent that from happening clear data->free_bitmaps in
snapshot_open() when the file is being opened for reading (hibernate

In addition to that, replace the BUG_ON() in free_basic_memory_bitmaps()
with a WARN_ON() as the kernel can continue just fine if the condition
checked by that macro occurs.

Fixes: aab172891542 (PM / hibernate: Fix user space driven resume regression)
Reported-by: Oliver Lorenz <>
Signed-off-by: Rafael J. Wysocki <>
Signed-off-by: Greg Kroah-Hartman <>

kernel/power/snapshot.c | 3 ++-
kernel/power/user.c | 1 +
2 files changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -792,7 +792,8 @@ void free_basic_memory_bitmaps(void)
struct memory_bitmap *bm1, *bm2;

- BUG_ON(!(forbidden_pages_map && free_pages_map));
+ if (WARN_ON(!(forbidden_pages_map && free_pages_map)))
+ return;

bm1 = forbidden_pages_map;
bm2 = free_pages_map;
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -70,6 +70,7 @@ static int snapshot_open(struct inode *i
data->swap = swsusp_resume_device ?
swap_type_of(swsusp_resume_device, 0, NULL) : -1;
data->mode = O_RDONLY;
+ data->free_bitmaps = false;
error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
if (error)

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