Currently, a file descriptor registered for preservation via the remains
globally registered with LUO until it is explicitly unregistered. This
creates a potential for resource leaks into the next kernel if the
userspace agent crashes or exits without proper cleanup before a live
update is fully initiated.

This patch ties the lifetime of FD preservation requests to the lifetime
of the open file descriptor for /dev/liveupdate, creating an implicit
"session".

When the /dev/liveupdate file descriptor is closed (either explicitly
via close() or implicitly on process exit/crash), the .release
handler, luo_release(), is now called. This handler invokes the new
function luo_unregister_all_files(), which iterates through all FDs
that were preserved through that session and unregisters them.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 kernel/liveupdate/luo_files.c    | 19 +++++++++++++++++++
 kernel/liveupdate/luo_internal.h |  1 +
 kernel/liveupdate/luo_ioctl.c    |  1 +
 3 files changed, 21 insertions(+)

diff --git a/kernel/liveupdate/luo_files.c b/kernel/liveupdate/luo_files.c
index 33577c9e9a64..63f8b086b785 100644
--- a/kernel/liveupdate/luo_files.c
+++ b/kernel/liveupdate/luo_files.c
@@ -721,6 +721,25 @@ int luo_unregister_file(u64 token)
 	return ret;
 }
 
+/**
+ * luo_unregister_all_files - Unpreserve all currently registered files.
+ *
+ * Iterates through all file descriptors currently registered for preservation
+ * and unregisters them, freeing all associated resources. This is typically
+ * called when LUO agent exits.
+ */
+void luo_unregister_all_files(void)
+{
+	struct luo_file *luo_file;
+	unsigned long token;
+
+	luo_state_read_enter();
+	xa_for_each(&luo_files_xa_out, token, luo_file)
+		__luo_unregister_file(token);
+	luo_state_read_exit();
+	WARN_ON_ONCE(atomic64_read(&luo_files_count) != 0);
+}
+
 /**
  * luo_retrieve_file - Find a registered file instance by its token.
  * @token: The unique token of the file instance to retrieve.
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index 5692196fd425..189e032d7738 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -37,5 +37,6 @@ void luo_do_subsystems_cancel_calls(void);
 int luo_retrieve_file(u64 token, struct file **filep);
 int luo_register_file(u64 token, int fd);
 int luo_unregister_file(u64 token);
+void luo_unregister_all_files(void);
 
 #endif /* _LINUX_LUO_INTERNAL_H */
diff --git a/kernel/liveupdate/luo_ioctl.c b/kernel/liveupdate/luo_ioctl.c
index 6f61569c94e8..7ca33d1c868f 100644
--- a/kernel/liveupdate/luo_ioctl.c
+++ b/kernel/liveupdate/luo_ioctl.c
@@ -137,6 +137,7 @@ static int luo_open(struct inode *inodep, struct file *filep)
 
 static int luo_release(struct inode *inodep, struct file *filep)
 {
+	luo_unregister_all_files();
 	atomic_set(&luo_device_in_use, 0);
 
 	return 0;
-- 
2.50.1.565.gc32cd1483b-goog