Commit 6a0c7cd3 authored Nov 14, 2013 by Rafael J. Wysocki

PM / Hibernate: Do not crash kernel in free_basic_memory_bitmaps()



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
mode).

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: aab17289 (PM / hibernate: Fix user space driven resume regression)
Reported-by: Oliver Lorenz <olli@olorenz.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: 3.12+ <stable@vger.kernel.org> # 3.12+

parent 5e01dc7b

kernel/power/snapshot.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -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;

kernel/power/user.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -70,6 +70,7 @@ static int snapshot_open(struct inode inode, struct file filp)
		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)
		pm_notifier_call_chain(PM_POST_HIBERNATION);

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