From 12a37b2ae19b1edabf390c0744ae0af9bb9d2b9a Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Thu, 3 Nov 2016 17:29:01 +0000
Subject: [PATCH] MdePkg/BaseMemoryLib*: check for zero length in ZeroMem ()

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, for all implementations of BaseMemoryLib
living under MdePkg/

This fixes an issue with the ARM implementation of BaseMemoryLibOPtDxe,
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>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
---
 MdePkg/Library/BaseMemoryLib/ZeroMemWrapper.c       | 6 +++++-
 MdePkg/Library/BaseMemoryLibMmx/ZeroMemWrapper.c    | 6 +++++-
 MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c | 6 +++++-
 MdePkg/Library/BaseMemoryLibOptPei/ZeroMemWrapper.c | 6 +++++-
 MdePkg/Library/BaseMemoryLibRepStr/ZeroMemWrapper.c | 6 +++++-
 MdePkg/Library/BaseMemoryLibSse2/ZeroMemWrapper.c   | 6 +++++-
 MdePkg/Library/PeiMemoryLib/ZeroMemWrapper.c        | 6 +++++-
 MdePkg/Library/UefiMemoryLib/ZeroMemWrapper.c       | 6 +++++-
 8 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/MdePkg/Library/BaseMemoryLib/ZeroMemWrapper.c b/MdePkg/Library/BaseMemoryLib/ZeroMemWrapper.c
index 2a0a038fd6..9dd0b45e18 100644
--- a/MdePkg/Library/BaseMemoryLib/ZeroMemWrapper.c
+++ b/MdePkg/Library/BaseMemoryLib/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);
 }
diff --git a/MdePkg/Library/BaseMemoryLibMmx/ZeroMemWrapper.c b/MdePkg/Library/BaseMemoryLibMmx/ZeroMemWrapper.c
index 2a0a038fd6..9dd0b45e18 100644
--- a/MdePkg/Library/BaseMemoryLibMmx/ZeroMemWrapper.c
+++ b/MdePkg/Library/BaseMemoryLibMmx/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);
 }
diff --git a/MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c b/MdePkg/Library/BaseMemoryLibOptDxe/ZeroMemWrapper.c
index 2a0a038fd6..9dd0b45e18 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);
 }
diff --git a/MdePkg/Library/BaseMemoryLibOptPei/ZeroMemWrapper.c b/MdePkg/Library/BaseMemoryLibOptPei/ZeroMemWrapper.c
index 2a0a038fd6..9dd0b45e18 100644
--- a/MdePkg/Library/BaseMemoryLibOptPei/ZeroMemWrapper.c
+++ b/MdePkg/Library/BaseMemoryLibOptPei/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);
 }
diff --git a/MdePkg/Library/BaseMemoryLibRepStr/ZeroMemWrapper.c b/MdePkg/Library/BaseMemoryLibRepStr/ZeroMemWrapper.c
index 2a0a038fd6..9dd0b45e18 100644
--- a/MdePkg/Library/BaseMemoryLibRepStr/ZeroMemWrapper.c
+++ b/MdePkg/Library/BaseMemoryLibRepStr/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);
 }
diff --git a/MdePkg/Library/BaseMemoryLibSse2/ZeroMemWrapper.c b/MdePkg/Library/BaseMemoryLibSse2/ZeroMemWrapper.c
index 2a0a038fd6..9dd0b45e18 100644
--- a/MdePkg/Library/BaseMemoryLibSse2/ZeroMemWrapper.c
+++ b/MdePkg/Library/BaseMemoryLibSse2/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);
 }
diff --git a/MdePkg/Library/PeiMemoryLib/ZeroMemWrapper.c b/MdePkg/Library/PeiMemoryLib/ZeroMemWrapper.c
index 5adddbbfad..a3aa7d10a6 100644
--- a/MdePkg/Library/PeiMemoryLib/ZeroMemWrapper.c
+++ b/MdePkg/Library/PeiMemoryLib/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);
 }
diff --git a/MdePkg/Library/UefiMemoryLib/ZeroMemWrapper.c b/MdePkg/Library/UefiMemoryLib/ZeroMemWrapper.c
index 5adddbbfad..a3aa7d10a6 100644
--- a/MdePkg/Library/UefiMemoryLib/ZeroMemWrapper.c
+++ b/MdePkg/Library/UefiMemoryLib/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);
 }
-- 
2.39.2