[PATCH 0/1] MR1821: bcrypt: Use volatile type cast to zero magic values before free.

[Paul Gofman (＠gofman)]

The compiler may optimize out the assignment before free and then
second free on the bcrypt handle finds magic values in the freed memory.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/1821

[PATCH 1/1] bcrypt: Use volatile type cast to zero magic values before free.

[Paul Gofman]

From: Paul Gofman <gofmanp(a)gmail.com>

The compiler may optimize out the assignment before free and then
second free on the bcrypt handle finds magic values in the freed memory.
---
 dlls/bcrypt/bcrypt_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dlls/bcrypt/bcrypt_main.c b/dlls/bcrypt/bcrypt_main.c
index 72501faf90e..d23a0328c55 100644
--- a/dlls/bcrypt/bcrypt_main.c
+++ b/dlls/bcrypt/bcrypt_main.c
@@ -397,7 +397,7 @@ NTSTATUS WINAPI BCryptOpenAlgorithmProvider( BCRYPT_ALG_HANDLE *handle, const WC
 
 static void destroy_object( struct object *obj )
 {
-    obj->magic = 0;
+    *(volatile int *)&obj->magic = 0;
     free( obj );
 }
 
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/1821

[PATCH 0/1] MR1821: bcrypt: Use volatile type cast to zero magic values before free. - approved

[Hans Leidekker (＠hans)]

This merge request was approved by Hans Leidekker.
-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/1821

[Alexandre Julliard (＠julliard)]

Maybe something like SecureZeroMemory() would make it more explicit?

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/1821#note_19686