From 43aea5c9402ff0a4c2bc8365ea9aa2ff3447a356 Mon Sep 17 00:00:00 2001
From: suzker <szhiliang@gmail.com>
Date: Tue, 24 May 2016 16:35:15 -0700
Subject: [PATCH 1/3] added filesize overflow check for mmap on 32bit os

---
 src/AbstractDiskWriter.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/AbstractDiskWriter.cc b/src/AbstractDiskWriter.cc
index 4d62bf97..df2d0a85 100644
--- a/src/AbstractDiskWriter.cc
+++ b/src/AbstractDiskWriter.cc
@@ -373,6 +373,14 @@ void AbstractDiskWriter::ensureMmapWrite(size_t len, int64_t offset)
         return;
       }
 
+      uint32_t filesize_lo = filesize & 0xffffffffu;
+      if (sizeof(off_t) > sizeof(size_t) && (filesize_lo) > 0) {
+        // filesize could overflow in 32bit OS with 64bit off_t type
+        // the filesize will be truncated if provided as a 32bit size_t
+        enableMmap_ = false;
+        return;
+      }
+
       int errNum = 0;
       if (static_cast<int64_t>(len + offset) <= filesize) {
 #ifdef __MINGW32__

From ef0a2e601f64904b87cf56244e5600a1c6baa3e9 Mon Sep 17 00:00:00 2001
From: suzker <szhiliang@gmail.com>
Date: Wed, 25 May 2016 07:43:57 -0700
Subject: [PATCH 2/3] Compare filesize directly to the numeric max of size_t

---
 src/AbstractDiskWriter.cc | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/AbstractDiskWriter.cc b/src/AbstractDiskWriter.cc
index df2d0a85..9e3dac4b 100644
--- a/src/AbstractDiskWriter.cc
+++ b/src/AbstractDiskWriter.cc
@@ -373,8 +373,7 @@ void AbstractDiskWriter::ensureMmapWrite(size_t len, int64_t offset)
         return;
       }
 
-      uint32_t filesize_lo = filesize & 0xffffffffu;
-      if (sizeof(off_t) > sizeof(size_t) && (filesize_lo) > 0) {
+      if (static_cast<uint64_t>(std::numeric_limits<size_t>::max()) < static_cast<uint64_t>(filesize)) {
         // filesize could overflow in 32bit OS with 64bit off_t type
         // the filesize will be truncated if provided as a 32bit size_t
         enableMmap_ = false;

From fa434319746e7ca9fb023cf8b1a4c1d0de67ed58 Mon Sep 17 00:00:00 2001
From: suzker <szhiliang@gmail.com>
Date: Fri, 27 May 2016 02:07:02 -0700
Subject: [PATCH 3/3] fixed mmap failure check with MAP_FAILED flag

---
 src/AbstractDiskWriter.cc | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/AbstractDiskWriter.cc b/src/AbstractDiskWriter.cc
index 9e3dac4b..a6191490 100644
--- a/src/AbstractDiskWriter.cc
+++ b/src/AbstractDiskWriter.cc
@@ -398,10 +398,14 @@ void AbstractDiskWriter::ensureMmapWrite(size_t len, int64_t offset)
           errNum = GetLastError();
         }
 #else  // !__MINGW32__
-        mapaddr_ = reinterpret_cast<unsigned char*>(mmap(
-            nullptr, filesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0));
-        if (!mapaddr_) {
+        void * pa = mmap(nullptr, filesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0);
+
+        if (pa == MAP_FAILED) {
           errNum = errno;
+          mapaddr_ = nullptr;
+        }
+        else {
+          mapaddr_ = reinterpret_cast<unsigned char*>(pa);
         }
 #endif // !__MINGW32__
         if (mapaddr_) {