Re: [PATCH 1/1] MdeModulePkg/UefiBootManagerLib: limit recursive call depth

["Wang, Sunny (HPS SW)" <sunnywang@hpe.com>]

Hi Heyi, 
Just a suggestion. 
Is it better to use a PCD instead of a define for MAX_RECONNECT_REPAIR? So that we can easily override it in our platform dsc file.

Regards,
Sunny Wang

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Heyi Guo
Sent: Monday, February 26, 2018 4:30 PM
To: edk2-devel@lists.01.org
Cc: Ruiyu Ni <ruiyu.ni@intel.com>; Heyi Guo <heyi.guo@linaro.org>; Eric Dong <eric.dong@intel.com>; Star Zeng <star.zeng@intel.com>
Subject: [edk2] [PATCH 1/1] MdeModulePkg/UefiBootManagerLib: limit recursive call depth

Function BmRepairAllControllers may recursively call itself if some driver health protocol returns EfiDriverHealthStatusReconnectRequired.
However, driver health protocol of some buggy third party driver may always return such status even after one and another reconnect. The endless iteration will cause stack overflow and then system exception, and it may be not easy to find that the exception is actually caused by stack overflow.

So we limit the number of reconnect retry to 10 to improve code robustness.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Heyi Guo <heyi.guo@linaro.org>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
---
 MdeModulePkg/Library/UefiBootManagerLib/InternalBm.h     |  6 ++++++
 MdeModulePkg/Library/UefiBootManagerLib/BmDriverHealth.c | 17 ++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Library/UefiBootManagerLib/InternalBm.h b/MdeModulePkg/Library/UefiBootManagerLib/InternalBm.h
index 25a1d522fe84..9aa86b096525 100644
--- a/MdeModulePkg/Library/UefiBootManagerLib/InternalBm.h
+++ b/MdeModulePkg/Library/UefiBootManagerLib/InternalBm.h
@@ -108,6 +108,12 @@ CHAR16 *
 #define BM_OPTION_NAME_LEN                          sizeof ("PlatformRecovery####")
 extern CHAR16  *mBmLoadOptionName[];
 
+//
+// Maximum number of reconnect retry to repair controller; it is to 
+limit the // number of recursive call of BmRepairAllControllers.
+//
+#define MAX_RECONNECT_REPAIR                        10
+
 /**
   Visitor function to be called by BmForEachVariable for each variable
   in variable storage.
diff --git a/MdeModulePkg/Library/UefiBootManagerLib/BmDriverHealth.c b/MdeModulePkg/Library/UefiBootManagerLib/BmDriverHealth.c
index ddcee8b0676f..30d70f32af84 100644
--- a/MdeModulePkg/Library/UefiBootManagerLib/BmDriverHealth.c
+++ b/MdeModulePkg/Library/UefiBootManagerLib/BmDriverHealth.c
@@ -26,6 +26,12 @@ GLOBAL_REMOVE_IF_UNREFERENCED
     L"Reboot Required"
     };
 
+//
+// Counter of reconnect retry to repair controller; it is to limit the 
+// number of recursive call of BmRepairAllControllers.
+//
+STATIC UINTN mReconnectRepairCount;
+
 /**
   Return the controller name.
 
@@ -549,7 +555,16 @@ BmRepairAllControllers (
 
 
   if (ReconnectRequired) {
-    BmRepairAllControllers ();
+    if (mReconnectRepairCount < MAX_RECONNECT_REPAIR) {
+      mReconnectRepairCount++;
+      BmRepairAllControllers ();
+    } else {
+      DEBUG ((DEBUG_ERROR, "[%a:%d] Repair failed after %d retries.\n",
+        __FUNCTION__, __LINE__, mReconnectRepairCount));
+      // Reset counter so that it will not affect calling
+      // BmRepairAllControllers() somewhere else
+      mReconnectRepairCount = 0;
+    }
   }
 
   DEBUG_CODE (
--
2.7.4

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