From: Matt Corallo <git@bluematt.me>
Date: Tue, 7 Mar 2023 18:06:12 +0000 (+0000)
Subject: Avoid `poll`ing completed futures in the `background-processor`
X-Git-Tag: v0.0.115~73^2
X-Git-Url: http://git.bitcoin.ninja/?a=commitdiff_plain;h=refs%2Fheads%2F2023-03-future-poll-panic;p=rust-lightning

Avoid `poll`ing completed futures in the `background-processor`

`poll`ing completed futures invokes undefined behavior in Rust
(panics, etc, obviously not memory corruption as its not unsafe).
Sadly, in our futures-based version of
`lightning-background-processor` we have one case where we can
`poll` a completed future - if the timer for the network graph
prune + persist completes without a network graph to prune +
persist we'll happily poll the same future over and over again,
likely panicing in user code.
---

diff --git a/lightning-background-processor/src/lib.rs b/lightning-background-processor/src/lib.rs
index a6de0a62f..d5b6d3f2c 100644
--- a/lightning-background-processor/src/lib.rs
+++ b/lightning-background-processor/src/lib.rs
@@ -349,9 +349,9 @@ macro_rules! define_run_body {
 						log_error!($logger, "Error: Failed to persist network graph, check your disk and permissions {}", e)
 					}
 
-					last_prune_call = $get_timer(NETWORK_PRUNE_TIMER);
 					have_pruned = true;
 				}
+				last_prune_call = $get_timer(NETWORK_PRUNE_TIMER);
 			}
 
 			if $timer_elapsed(&mut last_scorer_persist_call, SCORER_PERSIST_TIMER) {