[PATCH v4 5/6] MdeModulePkg/Core: prevent re-acquire GCD memory lock

[Jian J Wang <jian.j.wang@intel.com>]

> v4 changes:
> a. add more comments from Laszlo

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 move the memory allocation in CoreGetMemorySpaceMap()
and CoreGetIoSpaceMap() 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>
---
 MdeModulePkg/Core/Dxe/Gcd/Gcd.c | 87 +++++++++++++++++++++++++++++------------
 1 file changed, 62 insertions(+), 25 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/Gcd/Gcd.c b/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
index d9c65a8045..f99d6bb933 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;
   }
 
-  CoreAcquireGcdMemoryLock ();
+  *NumberOfDescriptors  = 0;
+  *MemorySpaceMap       = NULL;
 
   //
-  // Count the number of descriptors
+  // Take the lock, for entering the loop with the lock held.
   //
-  *NumberOfDescriptors = CoreCountGcdMapEntry (&mGcdMemorySpaceMap);
+  CoreAcquireGcdMemoryLock ();
+  while (TRUE) {
+    //
+    // Count the number of descriptors. It might be done more than once because
+    // there's code which 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;
+    }
 
-  //
-  // Allocate the MemorySpaceMap
-  //
-  *MemorySpaceMap = AllocatePool (*NumberOfDescriptors * sizeof (EFI_GCD_MEMORY_SPACE_DESCRIPTOR));
-  if (*MemorySpaceMap == NULL) {
-    Status = EFI_OUT_OF_RESOURCES;
-    goto Done;
-  }
+    //
+    // Release the lock before memory allocation, because it might cause
+    // GCD lock conflict in one of calling path in AllocatPool().
+    //
+    CoreReleaseGcdMemoryLock ();
+
+    //
+    // 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;
 }
 
 
-- 
2.16.2.windows.1