[PATCH v2 2/2] liveupdate: reject nonzero reserved value for SESSION_FINISH

[Jackie Liu <liu.yun@linux.dev>]

From: Jackie Liu <liuyun01@kylinos.cn>

The UAPI documents liveupdate_session_finish::reserved as requiring zero,
but luo_session_finish() currently ignores it and finishes the session.
Accepting nonzero values prevents the field from being safely repurposed
by a future extension.

Reject nonzero reserved values before changing session state, matching
LIVEUPDATE_SESSION_GET_NAME.

Fixes: 16cec0d26521 ("liveupdate: luo_session: add ioctls for file preservation")
Assisted-by: Codex:gpt-5.6-sol
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
---
 kernel/liveupdate/luo_session.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index f38b5b18f3f8..15342c0783b5 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -316,7 +316,12 @@ static int luo_session_finish(struct luo_session *session,
 			      struct luo_ucmd *ucmd)
 {
 	struct liveupdate_session_finish *argp = ucmd->cmd;
-	int err = luo_session_finish_one(session);
+	int err;
+
+	if (argp->reserved)
+		return -EINVAL;
+
+	err = luo_session_finish_one(session);
 
 	if (err)
 		return err;
-- 
2.54.0