[PATCH 1/2] liveupdate: luo_file: do not clear serialized_data on unfreeze

[Pratyush Yadav <pratyush@kernel.org>]

From: "Pratyush Yadav (Google)" <pratyush@kernel.org>

The unfreeze operation is supposed to undo the effects of the freeze
operation. serialized_data is not set by freeze, but by preserve.
Consequently, the unpreserve operation needs to access serialized_data
to undo the effects of the preserve operation. This includes freeing
the serialized data structures for example.

If a freeze callback fails, unfreeze is called for all frozen files.
This would clear serialized_data for them. Since live update has failed,
it can be expected that userspace aborts, releasing all sessions. When
the sessions are released, unpreserve will be called for all files. The
unfrozen files will see 0 in their serialized_data. This is not expected
by file handlers, and they might either fail, leaking data and state, or
might even crash or cause invalid memory access.

Do not clear serialized_data on unfreeze so it gets passed on to
unpreserve. There is no need to clear it on unpreserve since luo_file
will be freed immediately after.

Fixes: 7c722a7f44e0 ("liveupdate: luo_file: implement file systems callbacks")
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
---
 kernel/liveupdate/luo_file.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index a32a777f6df8..9f7283379ebc 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -402,8 +402,6 @@ static void luo_file_unfreeze_one(struct luo_file_set *file_set,
 
 		luo_file->fh->ops->unfreeze(&args);
 	}
-
-	luo_file->serialized_data = 0;
 }
 
 static void __luo_file_unfreeze(struct luo_file_set *file_set,
-- 
2.52.0.457.g6b5491de43-goog