From 7a29b1e4fdad6f523fe154bf8971a79cd646871e Mon Sep 17 00:00:00 2001
From: Daniel Pouzzner <douzzer@wolfssl.com>
Date: Wed, 14 Aug 2024 15:23:48 -0500
Subject: [PATCH] add comments explaining dependence on idempotency for
 race-free dynamics re checkedAESNI, haveAESNI, intel_flags, and sha_method. 
 see #7863.

---
 wolfcrypt/src/aes.c    | 4 ++++
 wolfcrypt/src/sha256.c | 4 ++++
 wolfcrypt/src/sha512.c | 4 ++++
 3 files changed, 12 insertions(+)

diff --git a/wolfcrypt/src/aes.c b/wolfcrypt/src/aes.c
index 93f91816b4..e3afa4a922 100644
--- a/wolfcrypt/src/aes.c
+++ b/wolfcrypt/src/aes.c
@@ -613,6 +613,10 @@ block cipher mechanism that uses n-bit binary string parameter key with 128-bits
         #define AESNI_ALIGN 16
     #endif
 
+    /* note that all write access to these static variables must be idempotent,
+     * as arranged by Check_CPU_support_AES(), else they will be susceptible to
+     * data races.
+     */
     static int checkedAESNI = 0;
     static int haveAESNI  = 0;
     static word32 intel_flags = 0;
diff --git a/wolfcrypt/src/sha256.c b/wolfcrypt/src/sha256.c
index 180a6c044b..2ba9ca62d1 100644
--- a/wolfcrypt/src/sha256.c
+++ b/wolfcrypt/src/sha256.c
@@ -408,6 +408,10 @@ static int InitSha256(wc_Sha256* sha256)
                        SHA256_SSE2, SHA256_C };
 
 #ifndef WC_C_DYNAMIC_FALLBACK
+    /* note that all write access to this static variable must be idempotent,
+     * as arranged by Sha256_SetTransform(), else it will be susceptible to
+     * data races.
+     */
     static enum sha_methods sha_method = SHA256_UNSET;
 #endif
 
diff --git a/wolfcrypt/src/sha512.c b/wolfcrypt/src/sha512.c
index 203267163a..77313f7a2a 100644
--- a/wolfcrypt/src/sha512.c
+++ b/wolfcrypt/src/sha512.c
@@ -489,6 +489,10 @@ static int InitSha512_256(wc_Sha512* sha512)
                        SHA512_AVX1_RORX, SHA512_AVX2_RORX, SHA512_C };
 
 #ifndef WC_C_DYNAMIC_FALLBACK
+    /* note that all write access to this static variable must be idempotent,
+     * as arranged by Sha512_SetTransform(), else it will be susceptible to
+     * data races.
+     */
     static enum sha_methods sha_method = SHA512_UNSET;
 #endif