From 0680f217ac7313e5df56ae90946e45206515729e Mon Sep 17 00:00:00 2001
From: Tennessee Carmel-Veilleux <tennessee.carmelveilleux@gmail.com>
Date: Fri, 15 Apr 2022 08:09:39 -0400
Subject: [PATCH] Allow SetGroupDataProvider(nullptr) for resource mgmt
 (#17408)

- Users implementing clean system shutdown must ensure that
  once they release their GroupDataProvider, the implementation
  does not dangle. After proper shutdown, GetGroupDataProvider()
  will never be called again, so it's fine to set it to nullptr.
  If it is indeed called, then next access will crash will null
  pointer dereference, which is more deterministic than use-after-free
  that would occur today.

- Allow setting GroupDataProvider singleton to nullptr

Testing done:
- Unit tests pass
- Integration tests pass
---
 src/credentials/GroupDataProvider.h       |  6 +++---
 src/credentials/GroupDataProviderImpl.cpp | 21 +--------------------
 2 files changed, 4 insertions(+), 23 deletions(-)

diff --git a/src/credentials/GroupDataProvider.h b/src/credentials/GroupDataProvider.h
index c9f0b64444edff..3c95f955b23edd 100644
--- a/src/credentials/GroupDataProvider.h
+++ b/src/credentials/GroupDataProvider.h
@@ -400,7 +400,7 @@ inline CHIP_ERROR SetSingleIpkEpochKey(GroupDataProvider * provider, FabricIndex
  *
  * Callers have to externally synchronize usage of this function.
  *
- * @return The global Group Data Provider. Assume never null.
+ * @return The global Group Data Provider
  */
 GroupDataProvider * GetGroupDataProvider();
 
@@ -409,9 +409,9 @@ GroupDataProvider * GetGroupDataProvider();
  *
  * Callers have to externally synchronize usage of this function.
  *
- * If the `provider` is nullptr, no change is done.
+ * The `provider` can be set to nullptr if the owner is done with it fully.
  *
- * @param[in] provider the Group Data Provider
+ * @param[in] provider pointer to the Group Data Provider global isntance to use
  */
 void SetGroupDataProvider(GroupDataProvider * provider);
 
diff --git a/src/credentials/GroupDataProviderImpl.cpp b/src/credentials/GroupDataProviderImpl.cpp
index 25367f83e28868..6047bfd3a45daa 100644
--- a/src/credentials/GroupDataProviderImpl.cpp
+++ b/src/credentials/GroupDataProviderImpl.cpp
@@ -2015,33 +2015,14 @@ GroupDataProvider * gGroupsProvider = nullptr;
 
 } // namespace
 
-/**
- * Instance getter for the global GroupDataProvider.
- *
- * Callers have to externally synchronize usage of this function.
- *
- * @return The global device attestation credentials provider. Assume never null.
- */
 GroupDataProvider * GetGroupDataProvider()
 {
     return gGroupsProvider;
 }
 
-/**
- * Instance setter for the global GroupDataProvider.
- *
- * Callers have to externally synchronize usage of this function.
- *
- * If the `provider` is nullptr, no change is done.
- *
- * @param[in] provider the GroupDataProvider to start returning with the getter
- */
 void SetGroupDataProvider(GroupDataProvider * provider)
 {
-    if (provider)
-    {
-        gGroupsProvider = provider;
-    }
+    gGroupsProvider = provider;
 }
 
 } // namespace Credentials