From 9751502ff5382dc0bc77d46fcff29a13419ef4fd Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Tue, 6 Dec 2022 05:35:04 +1030
Subject: [PATCH] jsonrpc: fix error when we abort batching due to timeout.

The read_json() call expects len_read to be the amount of *new*
data read.  If we call this back without resetting, it will parse
this much random junk in the buffer.

Fixes: #5766
Changelog-Fixed: Plugin: `autoclean` could misperform or get killed due to lightningd's invalid handling of JSON batching.
---
 lightningd/jsonrpc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lightningd/jsonrpc.c b/lightningd/jsonrpc.c
index b311f50da..13a757ed2 100644
--- a/lightningd/jsonrpc.c
+++ b/lightningd/jsonrpc.c
@@ -1109,6 +1109,8 @@ again:
 							  start_time),
 					 time_from_msec(250))) {
 				db_commit_transaction(jcon->ld->wallet->db);
+				/* Call us back, as if we read nothing new */
+				jcon->len_read = 0;
 				return io_always(conn, read_json, jcon);
 			}
 		}