From 6ee62a43abe7d7e77226415b21d1cbf16dbda85a Mon Sep 17 00:00:00 2001
From: Ben Harris <bjh21@bjh21.me.uk>
Date: Sun, 26 Feb 2023 21:48:10 +0000
Subject: [PATCH] Correctly handle some short save files

A save file that ended in the middle of a value before the "SAVEFILE"
field had been loaded would cause a read from uninitialised memory.
While technically undefined behaviour this was practically pretty
harmless.  Fixed by handling unexpected EOF here the same an
unexpected EOF anywhere else.

This bug could be demonstrated by loading a truncated save file like
this in a build with MemorySanitizer enabled:

SAVEFILE:41:Simo
---
 midend.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/midend.c b/midend.c
index 2365258..90bcde2 100644
--- a/midend.c
+++ b/midend.c
@@ -2340,7 +2340,7 @@ static const char *midend_deserialise_internal(
 
         val = snewn(len+1, char);
         if (!read(rctx, val, len)) {
-            if (started)
+            /* unexpected EOF */
             goto cleanup;
         }
         val[len] = '\0';
@@ -2747,7 +2747,7 @@ const char *identify_game(char **name,
 
         val = snewn(len+1, char);
         if (!read(rctx, val, len)) {
-            if (started)
+            /* unexpected EOF */
             goto cleanup;
         }
         val[len] = '\0';