The functions UsbHcGetPciAddressForHostMem and UsbHcFreeMem do have

ASSERT ((Block != NULL));

statements 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.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4210
Signed-off-by: Ranbir Singh <Ranbir.Singh3@Dell.com>
---
MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c b/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c
index 0a3ceb9f71..79575b6f63 100644
--- a/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c
+++ b/MdeModulePkg/Bus/Pci/EhciDxe/UsbHcMem.c
@@ -250,6 +250,11 @@ UsbHcGetPciAddressForHostMem (
}

ASSERT ((Block != NULL));
+
+  if (Block == NULL) {
+    return 0;
+  }
+
//
// calculate the pci memory address for host memory address.
//
@@ -536,6 +541,10 @@ UsbHcFreeMem (
//
ASSERT (Block != NULL);

+  if (Block == NULL) {
+    return;
+  }
+
//
// Release the current memory block if it is empty and not the head
//
--
2.36.1.windows.1