Re: [PATCH] CryptoPkg/BaseCryptLib: Fix potential integer overflow issue.

["Ye, Ting" <ting.ye@intel.com>]

Reviewed-by: Ye Ting <ting.ye@intel.com> 

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Long Qin
Sent: Wednesday, October 24, 2018 9:22 PM
To: edk2-devel@lists.01.org
Cc: Ye, Ting <ting.ye@intel.com>
Subject: [edk2] [PATCH] CryptoPkg/BaseCryptLib: Fix potential integer overflow issue.

The LookupFreeMemRegion() in RuntimeMemAllocate.c is used to look-up free memory region for runtime resource allocation, which was designed to support runtime authenticated variable service.
The direct offset subtractions in this function may bring possible integer overflow issue.

This patch is to add the extra parameter checks to remove this possible overflow risk.

Cc: Ye Ting <ting.ye@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Long Qin <qin.long@intel.com>
---
 .../Library/BaseCryptLib/SysCall/RuntimeMemAllocation.c    | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/CryptoPkg/Library/BaseCryptLib/SysCall/RuntimeMemAllocation.c b/CryptoPkg/Library/BaseCryptLib/SysCall/RuntimeMemAllocation.c
index 463f2bf855..92bb9ddccd 100644
--- a/CryptoPkg/Library/BaseCryptLib/SysCall/RuntimeMemAllocation.c
+++ b/CryptoPkg/Library/BaseCryptLib/SysCall/RuntimeMemAllocation.c
@@ -2,7 +2,7 @@
   Light-weight Memory Management Routines for OpenSSL-based Crypto
   Library at Runtime Phase.
 
-Copyright (c) 2009 - 2017, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2009 - 2018, Intel Corporation. All rights reserved.<BR>
 This program and the accompanying materials  are licensed and made available under the terms and conditions of the BSD License  which accompanies this distribution.  The full text of the license may be found at @@ -141,6 +141,12 @@ LookupFreeMemRegion (
 
   StartPageIndex = RT_SIZE_TO_PAGES (mRTPageTable->LastEmptyPageOffset);
   ReqPages       = RT_SIZE_TO_PAGES (AllocationSize);
+  if (ReqPages > mRTPageTable->PageCount) {
+    //
+    // No enough region for object allocation.
+    //
+    return (UINTN)(-1);
+  }
 
   //
   // Look up the free memory region with in current memory map table.
@@ -176,6 +182,12 @@ LookupFreeMemRegion (
   // Look up the free memory region from the beginning of the memory table
   // until the StartCursorOffset
   //
+  if (ReqPages > StartPageIndex) {
+    //
+    // No enough region for object allocation.
+    //
+    return (UINTN)(-1);
+  }
   for (Index = 0; Index < (StartPageIndex - ReqPages); ) {
     //
     // Check Consecutive ReqPages Pages.
--
2.16.1.windows.1

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