Revert "Check for success of decodes to avoid infinite loops"

This reverts commit dca380ffe0571be4023b11b06b8aecad9934bb06.

Reason for revert: Causes missing text in a user's PDF

Original change's description:
> Check for success of decodes to avoid infinite loops
> 
> Bug: 790693
> Change-Id: I9b1d87e024229d8b01f55ec554e2cc544db6ac06
> Reviewed-on: https://pdfium-review.googlesource.com/20230
> Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
> Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>

TBR=npm@chromium.org,hnakashima@chromium.org,rharrison@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 790693
Change-Id: I886b14e120c34da757a96f8a1f9c6a081d8326b6
Reviewed-on: https://pdfium-review.googlesource.com/22950
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>

4 files changed, 26 insertions, 44 deletions

diff --git a/core/fxcodec/jbig2/JBig2_ArithIntDecoder.cpp b/core/fxcodec/jbig2/JBig2_ArithIntDecoder.cpp
index 8ef1e0dc45..7ed7702964 100644
--- a/core/fxcodec/jbig2/JBig2_ArithIntDecoder.cpp
+++ b/core/fxcodec/jbig2/JBig2_ArithIntDecoder.cpp
@@ -53,9 +53,6 @@ bool CJBig2_ArithIntDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
   // Decoding Procedure" on page 113 of the JBIG2 specification (ISO/IEC FCD
   // 14492).
   int PREV = 1;
-  if (pArithDecoder->IsComplete())
-    return false;
-
   const int S = pArithDecoder->DECODE(&m_IAx[PREV]);
   PREV = ShiftOr(PREV, S);
 
@@ -64,9 +61,6 @@ bool CJBig2_ArithIntDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
 
   int nTemp = 0;
   for (int i = 0; i < g_ArithIntDecodeData[nDecodeDataIndex].nNeedBits; ++i) {
-    if (pArithDecoder->IsComplete())
-      return false;
-
     int D = pArithDecoder->DECODE(&m_IAx[PREV]);
     PREV = ShiftOr(PREV, D);
     if (PREV >= 256)
@@ -98,17 +92,13 @@ CJBig2_ArithIaidDecoder::CJBig2_ArithIaidDecoder(unsigned char SBSYMCODELENA)
 
 CJBig2_ArithIaidDecoder::~CJBig2_ArithIaidDecoder() {}
 
-bool CJBig2_ArithIaidDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
+void CJBig2_ArithIaidDecoder::decode(CJBig2_ArithDecoder* pArithDecoder,
                                      uint32_t* nResult) {
   int PREV = 1;
   for (unsigned char i = 0; i < SBSYMCODELEN; ++i) {
     JBig2ArithCtx* pCX = &m_IAID[PREV];
-    if (pArithDecoder->IsComplete())
-      return false;
-
     int D = pArithDecoder->DECODE(pCX);
     PREV = ShiftOr(PREV, D);
   }
   *nResult = PREV - (1 << SBSYMCODELEN);
-  return true;
 }
diff --git a/core/fxcodec/jbig2/JBig2_ArithIntDecoder.h b/core/fxcodec/jbig2/JBig2_ArithIntDecoder.h
index 2de42a09ee..fd9fa89f19 100644
--- a/core/fxcodec/jbig2/JBig2_ArithIntDecoder.h
+++ b/core/fxcodec/jbig2/JBig2_ArithIntDecoder.h
@@ -17,7 +17,8 @@ class CJBig2_ArithIntDecoder {
   CJBig2_ArithIntDecoder();
   ~CJBig2_ArithIntDecoder();
 
-  // Returns true on success, and false when an OOB condition occurs.
+  // Returns true on success, and false when an OOB condition occurs. Many
+  // callers can tolerate OOB and do not check the return value.
   bool decode(CJBig2_ArithDecoder* pArithDecoder, int* nResult);
 
  private:
@@ -29,7 +30,7 @@ class CJBig2_ArithIaidDecoder {
   explicit CJBig2_ArithIaidDecoder(unsigned char SBSYMCODELENA);
   ~CJBig2_ArithIaidDecoder();
 
-  bool decode(CJBig2_ArithDecoder* pArithDecoder, uint32_t* nResult);
+  void decode(CJBig2_ArithDecoder* pArithDecoder, uint32_t* nResult);
 
  private:
   std::vector<JBig2ArithCtx> m_IAID;
diff --git a/core/fxcodec/jbig2/JBig2_SddProc.cpp b/core/fxcodec/jbig2/JBig2_SddProc.cpp
index ee0c0f37f3..a446dbc6c0 100644
--- a/core/fxcodec/jbig2/JBig2_SddProc.cpp
+++ b/core/fxcodec/jbig2/JBig2_SddProc.cpp
@@ -68,9 +68,7 @@ std::unique_ptr<CJBig2_SymbolDict> CJBig2_SDDProc::decode_Arith(
   NSYMSDECODED = 0;
   while (NSYMSDECODED < SDNUMNEWSYMS) {
     std::unique_ptr<CJBig2_Image> BS;
-    if (!IADH->decode(pArithDecoder, &HCDH))
-      return nullptr;
-
+    IADH->decode(pArithDecoder, &HCDH);
     HCHEIGHT = HCHEIGHT + HCDH;
     if ((int)HCHEIGHT < 0 || (int)HCHEIGHT > JBIG2_MAX_IMAGE_SIZE)
       return nullptr;
@@ -115,8 +113,7 @@ std::unique_ptr<CJBig2_SymbolDict> CJBig2_SDDProc::decode_Arith(
         if (!BS)
           return nullptr;
       } else {
-        if (!IAAI->decode(pArithDecoder, reinterpret_cast<int*>(&REFAGGNINST)))
-          return nullptr;
+        IAAI->decode(pArithDecoder, (int*)&REFAGGNINST);
         if (REFAGGNINST > 1) {
           auto pDecoder = pdfium::MakeUnique<CJBig2_TRDProc>();
           pDecoder->SBHUFF = SDHUFF;
@@ -189,11 +186,12 @@ std::unique_ptr<CJBig2_SymbolDict> CJBig2_SDDProc::decode_Arith(
         } else if (REFAGGNINST == 1) {
           SBNUMSYMS = SDNUMINSYMS + NSYMSDECODED;
           uint32_t IDI;
-          if (!IAID->decode(pArithDecoder, &IDI) ||
-              !IARDX->decode(pArithDecoder, &RDXI) ||
-              !IARDY->decode(pArithDecoder, &RDYI) || IDI >= SBNUMSYMS) {
+          IAID->decode(pArithDecoder, &IDI);
+          IARDX->decode(pArithDecoder, &RDXI);
+          IARDY->decode(pArithDecoder, &RDYI);
+          if (IDI >= SBNUMSYMS)
             return nullptr;
-          }
+
           SBSYMS.resize(SBNUMSYMS);
           std::copy(SDINSYMS, SDINSYMS + SDNUMINSYMS, SBSYMS.begin());
           for (size_t i = 0; i < NSYMSDECODED; ++i)
@@ -227,10 +225,10 @@ std::unique_ptr<CJBig2_SymbolDict> CJBig2_SDDProc::decode_Arith(
   EXFLAGS.resize(SDNUMINSYMS + SDNUMNEWSYMS);
   num_ex_syms = 0;
   while (EXINDEX < SDNUMINSYMS + SDNUMNEWSYMS) {
-    if (!IAEX->decode(pArithDecoder, (int*)&EXRUNLENGTH) ||
-        EXINDEX + EXRUNLENGTH > SDNUMINSYMS + SDNUMNEWSYMS) {
+    IAEX->decode(pArithDecoder, (int*)&EXRUNLENGTH);
+    if (EXINDEX + EXRUNLENGTH > SDNUMINSYMS + SDNUMNEWSYMS)
       return nullptr;
-    }
+
     if (EXRUNLENGTH != 0) {
       for (I = EXINDEX; I < EXINDEX + EXRUNLENGTH; I++) {
         if (CUREXFLAG)
diff --git a/core/fxcodec/jbig2/JBig2_TrdProc.cpp b/core/fxcodec/jbig2/JBig2_TrdProc.cpp
index 78eb78012a..332e5868ac 100644
--- a/core/fxcodec/jbig2/JBig2_TrdProc.cpp
+++ b/core/fxcodec/jbig2/JBig2_TrdProc.cpp
@@ -281,9 +281,7 @@ std::unique_ptr<CJBig2_Image> CJBig2_TRDProc::decode_Arith(
     for (;;) {
       if (bFirst) {
         int32_t DFS;
-        if (!pIAFS->decode(pArithDecoder, &DFS))
-          return nullptr;
-
+        pIAFS->decode(pArithDecoder, &DFS);
         FIRSTS += DFS;
         CURS = FIRSTS;
         bFirst = false;
@@ -299,10 +297,8 @@ std::unique_ptr<CJBig2_Image> CJBig2_TRDProc::decode_Arith(
         break;
 
       int CURT = 0;
-      if (SBSTRIPS != 1) {
-        if (!pIAIT->decode(pArithDecoder, &CURT))
-          return nullptr;
-      }
+      if (SBSTRIPS != 1)
+        pIAIT->decode(pArithDecoder, &CURT);
 
       FX_SAFE_INT32 SAFE_TI = STRIPT + CURT;
       if (!SAFE_TI.IsValid())
@@ -310,16 +306,15 @@ std::unique_ptr<CJBig2_Image> CJBig2_TRDProc::decode_Arith(
 
       int32_t TI = SAFE_TI.ValueOrDie();
       uint32_t IDI;
-      if (!pIAID->decode(pArithDecoder, &IDI) || IDI >= SBNUMSYMS)
+      pIAID->decode(pArithDecoder, &IDI);
+      if (IDI >= SBNUMSYMS)
         return nullptr;
 
       int RI;
-      if (SBREFINE == 0) {
+      if (SBREFINE == 0)
         RI = 0;
-      } else {
-        if (!pIARI->decode(pArithDecoder, &RI))
-          return nullptr;
-      }
+      else
+        pIARI->decode(pArithDecoder, &RI);
 
       MaybeOwned<CJBig2_Image> pIBI;
       if (RI == 0) {
@@ -329,12 +324,10 @@ std::unique_ptr<CJBig2_Image> CJBig2_TRDProc::decode_Arith(
         int32_t RDHI;
         int32_t RDXI;
         int32_t RDYI;
-        if (!pIARDW->decode(pArithDecoder, &RDWI) ||
-            !pIARDH->decode(pArithDecoder, &RDHI) ||
-            !pIARDX->decode(pArithDecoder, &RDXI) ||
-            !pIARDY->decode(pArithDecoder, &RDYI)) {
-          return nullptr;
-        }
+        pIARDW->decode(pArithDecoder, &RDWI);
+        pIARDH->decode(pArithDecoder, &RDHI);
+        pIARDX->decode(pArithDecoder, &RDXI);
+        pIARDY->decode(pArithDecoder, &RDYI);
         CJBig2_Image* IBOI = SBSYMS[IDI];
         if (!IBOI)
           return nullptr;