From 5c8aa89163fabc0496c96deeabd3775b2c9116cc Mon Sep 17 00:00:00 2001
From: Juan Lang <juan.lang@gmail.com>
Date: Mon, 14 Jan 2008 11:15:35 -0800
Subject: [PATCH] crypt32: Fix race condition in loading default provider.

---
 dlls/crypt32/main.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/dlls/crypt32/main.c b/dlls/crypt32/main.c
index fa90ee05726..922dd1955a7 100644
--- a/dlls/crypt32/main.c
+++ b/dlls/crypt32/main.c
@@ -59,8 +59,16 @@ BOOL WINAPI DllMain(HINSTANCE hInstance, DWORD fdwReason, PVOID pvReserved)
 HCRYPTPROV CRYPT_GetDefaultProvider(void)
 {
     if (!hDefProv)
-        CryptAcquireContextW(&hDefProv, NULL, MS_ENHANCED_PROV_W,
-         PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
+    {
+        HCRYPTPROV prov;
+
+        CryptAcquireContextW(&prov, NULL, MS_ENHANCED_PROV_W, PROV_RSA_FULL,
+         CRYPT_VERIFYCONTEXT);
+        InterlockedCompareExchangePointer((PVOID *)&hDefProv, (PVOID)prov,
+         NULL);
+        if (hDefProv != prov)
+            CryptReleaseContext(prov, 0);
+    }
     return hDefProv;
 }