From 2d168b0516f7f1a70f8dba262d2ea8bbd4018b95 Mon Sep 17 00:00:00 2001
From: Daniel Micay <danielmicay@gmail.com>
Date: Fri, 24 Aug 2018 04:51:52 -0400
Subject: [PATCH] check for double free slightly earlier

---
 malloc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/malloc.c b/malloc.c
index 0832937..3263371 100644
--- a/malloc.c
+++ b/malloc.c
@@ -387,6 +387,10 @@ static void slab_free(void *p) {
         fatal_error("invalid unaligned free");
     }
 
+    if (!get_slot(metadata, slot)) {
+        fatal_error("double free");
+    }
+
     if (!has_free_slots(slots, metadata)) {
         metadata->next = c->partial_slabs;
         metadata->prev = NULL;
@@ -397,9 +401,6 @@ static void slab_free(void *p) {
         c->partial_slabs = metadata;
     }
 
-    if (!get_slot(metadata, slot)) {
-        fatal_error("double free");
-    }
     clear_slot(metadata, slot);
     memset(p, 0, size);