[PATCH v1 1/1] MdeModulePkg/Bus/Pci/EhciDxe: Fix FORWARD_NULL Coverity issues

[Ranbir Singh <rsingh@ventanamicro.com>]

From: Ranbir Singh <Ranbir.Singh3@Dell.com>

The function UsbHcGetPciAddressForHostMem has

    ASSERT ((Block != NULL));

and the UsbHcFreeMem has

    ASSERT (Block != NULL);

statement after for loop, but these are applicable only in DEBUG mode.
In RELEASE mode, if for whatever reasons there is no match inside for
loop and the loop exits because of Block != NULL; condition, then there
is no "Block" NULL pointer check afterwards and the code proceeds to do
dereferencing "Block" which will lead to CRASH.

Hence, for safety add NULL pointer checks always.

Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4210
Signed-off-by: Ranbir Singh <Ranbir.Singh3@Dell.com>
Signed-off-by: Ranbir Singh <rsingh@ventanamicro.com>
---
 MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c b/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c
index 0a3ceb9f711a..623cca0d7eb3 100644
--- a/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c
+++ b/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c
@@ -250,6 +250,12 @@ UsbHcGetPciAddressForHostMem (
   }
 
   ASSERT ((Block != NULL));
+
+  if (Block == NULL) {
+    DEBUG ((DEBUG_INFO, "Given memory block not present in host controller's pool\n"));
+    return 0;
+  }
+
   //
   // calculate the pci memory address for host memory address.
   //
@@ -536,6 +542,11 @@ UsbHcFreeMem (
   //
   ASSERT (Block != NULL);
 
+  if (Block == NULL) {
+    DEBUG ((DEBUG_INFO, "Memory to free not present in host controller's pool\n"));
+    return;
+  }
+
   //
   // Release the current memory block if it is empty and not the head
   //
-- 
2.34.1