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diff --git a/include/exiv2/value.hpp b/include/exiv2/value.hpp
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index 64a8ca7..4e9f285 100644
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--- a/include/exiv2/value.hpp
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+++ b/include/exiv2/value.hpp
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@@ -1658,11 +1658,13 @@ namespace Exiv2 {
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         ok_ = true;
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         return static_cast<long>(value_[n]);
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     }
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+// #55 crash when value_[n].first == LONG_MIN
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+#define LARGE_INT 1000000
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     // Specialization for rational
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     template<>
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     inline long ValueType<Rational>::toLong(long n) const
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     {
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-        ok_ = (value_[n].second != 0);
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+        ok_ = (value_[n].second != 0 && -LARGE_INT < value_[n].first && value_[n].first < LARGE_INT);
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         if (!ok_) return 0;
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         return value_[n].first / value_[n].second;
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     }
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@@ -1670,7 +1672,7 @@ namespace Exiv2 {
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     template<>
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     inline long ValueType<URational>::toLong(long n) const
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     {
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-        ok_ = (value_[n].second != 0);
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+        ok_ = (value_[n].second != 0 && value_[n].first < LARGE_INT);
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         if (!ok_) return 0;
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         return value_[n].first / value_[n].second;
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     }
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diff --git a/src/basicio.cpp b/src/basicio.cpp
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index 1ede931..eac756f 100644
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--- a/src/basicio.cpp
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+++ b/src/basicio.cpp
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@@ -990,6 +990,7 @@ namespace Exiv2 {
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     DataBuf FileIo::read(long rcount)
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     {
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         assert(p_->fp_ != 0);
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+        if ( (size_t) rcount > size() ) throw Error(57);
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         DataBuf buf(rcount);
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         long readCount = read(buf.pData_, buf.size_);
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         buf.size_ = readCount;
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diff --git a/src/image.cpp b/src/image.cpp
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index 31b9b81..eeb1f37 100644
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--- a/src/image.cpp
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+++ b/src/image.cpp
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@@ -399,7 +399,13 @@ namespace Exiv2 {
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                                 ;
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                 // if ( offset > io.size() ) offset = 0; // Denial of service?
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-                DataBuf  buf(size*count + pad+20);  // allocate a buffer
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+
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+                // #55 memory allocation crash test/data/POC8
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+                long long allocate = (long long) size*count + pad+20;
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+                if ( allocate > (long long) io.size() ) {
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+                    throw Error(57);
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+                }
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+                DataBuf  buf(allocate);  // allocate a buffer
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                 std::memcpy(buf.pData_,dir.pData_+8,4);  // copy dir[8:11] into buffer (short strings)
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                 if ( count*size > 4 ) {            // read into buffer
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                     size_t   restore = io.tell();  // save