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deps: fix out-of-band write in utf8 decoder
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Originally reported by: Kris Reeves <[email protected]>

This is a back-port of commit 030f804 from the master branch.

Reviewed-By: Rod Vagg <[email protected]>
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bnoordhuis authored and rvagg committed Jul 4, 2015
1 parent d8f260d commit 78de5f8
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Showing 2 changed files with 13 additions and 5 deletions.
10 changes: 8 additions & 2 deletions deps/v8/src/unicode-decoder.cc
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ void Utf8DecoderBase::Reset(uint16_t* buffer, unsigned buffer_length,
// Assume everything will fit in the buffer and stream won't be needed.
last_byte_of_buffer_unused_ = false;
unbuffered_start_ = NULL;
unbuffered_length_ = 0;
bool writing_to_buffer = true;
// Loop until stream is read, writing to buffer as long as buffer has space.
unsigned utf16_length = 0;
Expand All @@ -41,6 +42,7 @@ void Utf8DecoderBase::Reset(uint16_t* buffer, unsigned buffer_length,
// Just wrote last character of buffer
writing_to_buffer = false;
unbuffered_start_ = stream;
unbuffered_length_ = stream_length;
}
continue;
}
Expand All @@ -50,19 +52,22 @@ void Utf8DecoderBase::Reset(uint16_t* buffer, unsigned buffer_length,
writing_to_buffer = false;
last_byte_of_buffer_unused_ = true;
unbuffered_start_ = stream - cursor;
unbuffered_length_ = stream_length + cursor;
}
utf16_length_ = utf16_length;
}


void Utf8DecoderBase::WriteUtf16Slow(const uint8_t* stream, uint16_t* data,
void Utf8DecoderBase::WriteUtf16Slow(const uint8_t* stream,
unsigned stream_length, uint16_t* data,
unsigned data_length) {
while (data_length != 0) {
unsigned cursor = 0;
uint32_t character = Utf8::ValueOf(stream, Utf8::kMaxEncodedSize, &cursor);
uint32_t character = Utf8::ValueOf(stream, stream_length, &cursor);
// There's a total lack of bounds checking for stream
// as it was already done in Reset.
stream += cursor;
stream_length -= cursor;
if (character > unibrow::Utf16::kMaxNonSurrogateCharCode) {
*data++ = Utf16::LeadSurrogate(character);
*data++ = Utf16::TrailSurrogate(character);
Expand All @@ -73,6 +78,7 @@ void Utf8DecoderBase::WriteUtf16Slow(const uint8_t* stream, uint16_t* data,
data_length -= 1;
}
}
DCHECK(stream_length >= 0);
}

} // namespace unibrow
8 changes: 5 additions & 3 deletions deps/v8/src/unicode-decoder.h
Original file line number Diff line number Diff line change
Expand Up @@ -23,9 +23,10 @@ class Utf8DecoderBase {
// The first buffer_length utf16 chars are cached in the buffer.
void Reset(uint16_t* buffer, unsigned buffer_length, const uint8_t* stream,
unsigned stream_length);
static void WriteUtf16Slow(const uint8_t* stream, uint16_t* data,
unsigned length);
static void WriteUtf16Slow(const uint8_t* stream, unsigned stream_length,
uint16_t* data, unsigned length);
const uint8_t* unbuffered_start_;
unsigned unbuffered_length_;
unsigned utf16_length_;
bool last_byte_of_buffer_unused_;

Expand All @@ -48,6 +49,7 @@ class Utf8Decoder : public Utf8DecoderBase {

Utf8DecoderBase::Utf8DecoderBase()
: unbuffered_start_(NULL),
unbuffered_length_(0),
utf16_length_(0),
last_byte_of_buffer_unused_(false) {}

Expand Down Expand Up @@ -85,7 +87,7 @@ unsigned Utf8Decoder<kBufferSize>::WriteUtf16(uint16_t* data,
if (length <= buffer_length) return length;
DCHECK(unbuffered_start_ != NULL);
// Copy the rest the slow way.
WriteUtf16Slow(unbuffered_start_, data + buffer_length,
WriteUtf16Slow(unbuffered_start_, unbuffered_length_, data + buffer_length,
length - buffer_length);
return length;
}
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