fix crash when reading malformed PCX images (#3836)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@54766 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/src/common/imagpcx.cpp b/src/common/imagpcx.cpp
index 69b04d1ea72c2b5bc69cb03ec84eca2f21ba5f81..05f1d66a5e5c9fc9df5d475e8f35d63b3df316bb 100644 (file)
--- a/src/common/imagpcx.cpp
+++ b/src/common/imagpcx.cpp
@@ -87,17 +87,15 @@ void RLEencode(unsigned char *p, unsigned int size, wxOutputStream& s)
 
 void RLEdecode(unsigned char *p, unsigned int size, wxInputStream& s)
 {
 
 void RLEdecode(unsigned char *p, unsigned int size, wxInputStream& s)
 {

-    unsigned int i, data, cont;
-

     // Read 'size' bytes. The PCX official specs say there will be
     // a decoding break at the end of each scanline (but not at the
     // end of each plane inside a scanline). Only use this function
     // to read one or more _complete_ scanlines. Else, more than
     // 'size' bytes might be read and the buffer might overflow.
 
     // Read 'size' bytes. The PCX official specs say there will be
     // a decoding break at the end of each scanline (but not at the
     // end of each plane inside a scanline). Only use this function
     // to read one or more _complete_ scanlines. Else, more than
     // 'size' bytes might be read and the buffer might overflow.
 

-    while (size > 0)
+    while (size != 0)

     {
     {

-        data = (unsigned char)s.GetC();
+        unsigned int data = (unsigned char)s.GetC();

 
         // If ((data & 0xC0) != 0xC0), then the value read is a data
         // byte. Else, it is a counter (cont = val & 0x3F) and the
 
         // If ((data & 0xC0) != 0xC0), then the value read is a data
         // byte. Else, it is a counter (cont = val & 0x3F) and the


@@ -110,9 +108,11 @@ void RLEdecode(unsigned char *p, unsigned int size, wxInputStream& s)
         }
         else
         {
         }
         else
         {

-            cont = data & 0x3F;
+            unsigned int cont = data & 0x3F;
+            if (cont > size) // can happen only if the file is malformed
+                break;

             data = (unsigned char)s.GetC();
             data = (unsigned char)s.GetC();

-            for (i = 1; i <= cont; i++)
+            for (unsigned int i = 1; i <= cont; i++)

                 *(p++) = (unsigned char)data;
             size -= cont;
         }
                 *(p++) = (unsigned char)data;
             size -= cont;
         }