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-rw-r--r--core/fxcodec/jbig2/JBig2_Context.cpp10
1 files changed, 10 insertions, 0 deletions
diff --git a/core/fxcodec/jbig2/JBig2_Context.cpp b/core/fxcodec/jbig2/JBig2_Context.cpp
index 57bae1c617..88c8cfa21c 100644
--- a/core/fxcodec/jbig2/JBig2_Context.cpp
+++ b/core/fxcodec/jbig2/JBig2_Context.cpp
@@ -689,6 +689,16 @@ int32_t CJBig2_Context::parseTextRegion(CJBig2_Segment* pSegment) {
if (m_pStream->readInteger(&pTRD->SBNUMINSTANCES) != 0)
return JBIG2_ERROR_TOO_SHORT;
+ // Assume each instance takes at least 4 bits. That means for a stream of
+ // length N, there can be at most 2N instances. This is an extremely
+ // conservative estimate just to sanitize the |SBNUMINSTANCES| value.
+ // Use FX_SAFE_INT32 to be safe, though it should never overflow because PDFs
+ // have a maximum size of roughly 11 GB.
+ FX_SAFE_INT32 nMaxStripInstances = m_pStream->getLength();
+ nMaxStripInstances *= 2;
+ if (pTRD->SBNUMINSTANCES > nMaxStripInstances.ValueOrDie())
+ return JBIG2_ERROR_FATAL;
+
for (int32_t i = 0; i < pSegment->m_nReferred_to_segment_count; ++i) {
if (!findSegmentByNumber(pSegment->m_Referred_to_segment_numbers[i]))
return JBIG2_ERROR_FATAL;