[PATCH v2] MdePkg/BaseMemoryLibOptDxe: check for zero length in ZeroMem ()

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

Unlike other string functions in this library, ZeroMem () does not
return early when the length of the input buffer is 0. So add the
same to ZeroMem () as well.

This fixes an issue with the ARM implementation, whose InternalMemZeroMem
code does not expect a length of 0, and always writes at least a single
byte.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c b/MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c
index 2a0a038fd6c5..9dd0b45e188e 100644
--- a/MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c
+++ b/MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c
@@ -46,7 +46,11 @@ ZeroMem (
   IN UINTN  Length
   )
 {
-  ASSERT (!(Buffer == NULL && Length > 0));
+  if (Length == 0) {
+    return Buffer;
+  }
+
+  ASSERT (Buffer != NULL);
   ASSERT (Length <= (MAX_ADDRESS - (UINTN)Buffer + 1));
   return InternalMemZeroMem (Buffer, Length);
 }
-- 
2.7.4