From bb685071c2602cf786ea84c69bbebf2158194a38 Mon Sep 17 00:00:00 2001
From: Jian J Wang <jian.j.wang@intel.com>
Date: Wed, 24 Oct 2018 11:28:32 +0800
Subject: [PATCH] MdeModulePkg/Core: prevent re-acquire GCD memory lock

This issue is hidden in current code but exposed by introduction
of freed-memory guard feature due to the fact that the feature
will turn all pool allocation to page allocation.

The solution is moving the memory allocation in CoreGetMemorySpaceMap()
to be out of the GCD memory map lock.

   CoreDumpGcdMemorySpaceMap()
=> CoreGetMemorySpaceMap()
=> CoreAcquireGcdMemoryLock () *
   AllocatePool()
=> InternalAllocatePool()
=> CoreAllocatePool()
=> CoreAllocatePoolI()
=> CoreAllocatePoolPagesI()
=> CoreAllocatePoolPages()
=> FindFreePages()
=> PromoteMemoryResource()
=> CoreAcquireGcdMemoryLock()  **

Cc: Star Zeng <star.zeng@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
---
 MdeModulePkg/Core/Dxe/Gcd/Gcd.c | 89 +++++++++++++++++++++++----------
 1 file changed, 63 insertions(+), 26 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/Gcd/Gcd.c b/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
index d9c65a8045..8bbdf7129f 100644
--- a/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
+++ b/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
@@ -1691,10 +1691,10 @@ CoreGetMemorySpaceMap (
   OUT EFI_GCD_MEMORY_SPACE_DESCRIPTOR  **MemorySpaceMap
   )
 {
-  EFI_STATUS                       Status;
   LIST_ENTRY                       *Link;
   EFI_GCD_MAP_ENTRY                *Entry;
   EFI_GCD_MEMORY_SPACE_DESCRIPTOR  *Descriptor;
+  UINTN                            DescriptorCount;
 
   //
   // Make sure parameters are valid
@@ -1706,38 +1706,75 @@ CoreGetMemorySpaceMap (
     return EFI_INVALID_PARAMETER;
   }
 
+  *NumberOfDescriptors  = 0;
+  *MemorySpaceMap       = NULL;
+
+  //
+  // Take the lock, for entering the loop with the lock held.
+  //
   CoreAcquireGcdMemoryLock ();
+  while (TRUE) {
+    //
+    // Count descriptors. It might be done more than once because the
+    // AllocatePool() called below has to be running outside the GCD lock.
+    //
+    DescriptorCount = CoreCountGcdMapEntry (&mGcdMemorySpaceMap);
+    if (DescriptorCount == *NumberOfDescriptors) {
+      //
+      // Fill in the MemorySpaceMap if no memory space map change.
+      //
+      Descriptor = *MemorySpaceMap;
+      Link = mGcdMemorySpaceMap.ForwardLink;
+      while (Link != &mGcdMemorySpaceMap) {
+        Entry = CR (Link, EFI_GCD_MAP_ENTRY, Link, EFI_GCD_MAP_SIGNATURE);
+        BuildMemoryDescriptor (Descriptor, Entry);
+        Descriptor++;
+        Link = Link->ForwardLink;
+      }
+      //
+      // We're done; exit the loop with the lock held.
+      //
+      break;
+    }
 
-  //
-  // Count the number of descriptors
-  //
-  *NumberOfDescriptors = CoreCountGcdMapEntry (&mGcdMemorySpaceMap);
+    //
+    // Release the lock before memory allocation, because it might cause
+    // GCD lock conflict in one of calling path in AllocatPool().
+    //
+    CoreReleaseGcdMemoryLock ();
 
-  //
-  // Allocate the MemorySpaceMap
-  //
-  *MemorySpaceMap = AllocatePool (*NumberOfDescriptors * sizeof (EFI_GCD_MEMORY_SPACE_DESCRIPTOR));
-  if (*MemorySpaceMap == NULL) {
-    Status = EFI_OUT_OF_RESOURCES;
-    goto Done;
+    //
+    // Allocate memory to store the MemorySpaceMap. Note it might be already
+    // allocated if there's map descriptor change during memory allocation at
+    // last time.
+    //
+    if (*MemorySpaceMap != NULL) {
+      FreePool (*MemorySpaceMap);
+    }
+
+    *MemorySpaceMap = AllocatePool (DescriptorCount *
+                                    sizeof (EFI_GCD_MEMORY_SPACE_DESCRIPTOR));
+    if (*MemorySpaceMap == NULL) {
+      *NumberOfDescriptors = 0;
+      return EFI_OUT_OF_RESOURCES;
+    }
+
+    //
+    // Save the descriptor count got before for another round of check to make
+    // sure we won't miss any, since we have code running outside the GCD lock.
+    //
+    *NumberOfDescriptors = DescriptorCount;
+    //
+    // Re-acquire the lock, for the next iteration.
+    //
+    CoreAcquireGcdMemoryLock ();
   }
-
   //
-  // Fill in the MemorySpaceMap
+  // We exited the loop with the lock held, release it.
   //
-  Descriptor = *MemorySpaceMap;
-  Link = mGcdMemorySpaceMap.ForwardLink;
-  while (Link != &mGcdMemorySpaceMap) {
-    Entry = CR (Link, EFI_GCD_MAP_ENTRY, Link, EFI_GCD_MAP_SIGNATURE);
-    BuildMemoryDescriptor (Descriptor, Entry);
-    Descriptor++;
-    Link = Link->ForwardLink;
-  }
-  Status = EFI_SUCCESS;
-
-Done:
   CoreReleaseGcdMemoryLock ();
-  return Status;
+
+  return EFI_SUCCESS;
 }