From 3e16e59f7246dde78182753b7df0e49e38c1bcda Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C5=8Dshin?= <git@wholezero.org>
Date: Wed, 10 Apr 2024 23:04:03 -0400
Subject: [PATCH] Move store after __asan_unpoison in __zipos_alloc (#1135)

Previously, the atomic store looked like it was happening while the
struct's memory was still poisoned. I was unable to observe any issues
with this, but this change seems to make the code more obviously correct
(at the cost of a redundant atomic store to zeroed space in case the map
needed to be extended.)
---
 libc/runtime/zipos-open.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libc/runtime/zipos-open.c b/libc/runtime/zipos-open.c
index 83b71ed76..d3bb03555 100644
--- a/libc/runtime/zipos-open.c
+++ b/libc/runtime/zipos-open.c
@@ -114,7 +114,6 @@ StartOver:
   while ((h = *ph)) {
     if (h->mapsize >= mapsize) {
       if (!_cmpxchg(ph, h, h->next)) goto StartOver;
-      atomic_store_explicit(&h->refs, 0, memory_order_relaxed);
       break;
     }
     ph = &h->next;
@@ -130,6 +129,7 @@ StartOver:
                   kAsanHeapOverrun);
   }
   if (h) {
+    atomic_store_explicit(&h->refs, 0, memory_order_relaxed);
     h->size = size;
     h->zipos = zipos;
     h->mapsize = mapsize;