From 123b720eeb371e0a31eb727bcf59255b584e355f Mon Sep 17 00:00:00 2001
From: Eric Dong <eric.dong@intel.com>
Date: Mon, 23 Dec 2019 14:37:28 +0800
Subject: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Fix buffer overflow issue.

The size for the array of mSmmMpSyncData->CpuData[] is 0 ~
mMaxNumberOfCpus -1. But current code may use
mSmmMpSyncData->CpuData[mMaxNumberOfCpus].

This patch fixed this issue.

Reviewed-by: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Eric Dong <eric.dong@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
index 35951cc43e..4808045f71 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -137,7 +137,7 @@ ReleaseAllAPs (
 {
   UINTN                             Index;
 
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       ReleaseSemaphore (mSmmMpSyncData->CpuData[Index].Run);
     }
@@ -170,7 +170,7 @@ AllCpusInSmmWithExceptions (
 
   CpuData = mSmmMpSyncData->CpuData;
   ProcessorInfo = gSmmCpuPrivate->ProcessorInfo;
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (!(*(CpuData[Index].Present)) && ProcessorInfo[Index].ProcessorId != INVALID_APIC_ID) {
       if (((Exceptions & ARRIVAL_EXCEPTION_DELAYED) != 0) && SmmCpuFeaturesGetSmmRegister (Index, SmmRegSmmDelayed) != 0) {
         continue;
@@ -305,7 +305,7 @@ SmmWaitForApArrival (
     //
     // Send SMI IPIs to bring outside processors in
     //
-    for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+    for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
       if (!(*(mSmmMpSyncData->CpuData[Index].Present)) && gSmmCpuPrivate->ProcessorInfo[Index].ProcessorId != INVALID_APIC_ID) {
         SendSmiIpi ((UINT32)gSmmCpuPrivate->ProcessorInfo[Index].ProcessorId);
       }
@@ -361,7 +361,7 @@ WaitForAllAPsNotBusy (
 {
   UINTN                             Index;
 
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     //
     // Ignore BSP and APs which not call in SMM.
     //
@@ -617,7 +617,7 @@ BSPHandler (
     //
     while (TRUE) {
       PresentCount = 0;
-      for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+      for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
         if (*(mSmmMpSyncData->CpuData[Index].Present)) {
           PresentCount ++;
         }
@@ -1301,7 +1301,7 @@ InternalSmmStartupAllAPs (
   }
 
   CpuCount = 0;
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       CpuCount ++;
 
@@ -1333,13 +1333,13 @@ InternalSmmStartupAllAPs (
   // Here code always use AcquireSpinLock instead of AcquireSpinLockOrFail for not
   // block mode.
   //
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       AcquireSpinLock (mSmmMpSyncData->CpuData[Index].Busy);
     }
   }
 
-  for (Index = mMaxNumberOfCpus; Index-- > 0;) {
+  for (Index = 0; Index < mMaxNumberOfCpus; Index++) {
     if (IsPresentAp (Index)) {
       mSmmMpSyncData->CpuData[Index].Procedure = (EFI_AP_PROCEDURE2) Procedure;
       mSmmMpSyncData->CpuData[Index].Parameter = ProcedureArguments;
-- 
2.39.2