[mythtv] Backend SEGV

[Marcus Metzler]

>>>>> "Daniel" == Daniel Kristjansson <danielk at cuymedia.net> writes:

    Daniel> On Wed, 2006-03-01 at 13:31 +0000, Stuart Auchterlonie
    Daniel> wrote:
    >> I'm having the backend segfault on 9218.  I believe it's
    >> related to [9214] as it is attempting to covert the ServiceName
    >> to a string using dvb_decode_text rather than the old
    >> copy. dvb_decode_text can't find a codec to decode this and
    >> returns a NULL codec.

    Daniel> Can you try SVN?

    Daniel> I believe this was due to an off-by-one error fixed in
    Daniel> commit 9219.

Since I only saw your fix after I fixed the problem for myself and I
would have to roll back everything to see if it works, I would like to
suggest to add the following diff to
mythtv/libs/libmythtv/mpeg/dvbdescriptors.cpp.
This adds some checks to the dvb_decode_text function that would avoid
segfaults. To see that there might be trouble in other function some
warning messages could be added instead of just returning N/A. 

Marcus



Index: dvbdescriptors.cpp
===================================================================
--- dvbdescriptors.cpp	(revision 9218)
+++ dvbdescriptors.cpp	(working copy)
@@ -12,16 +12,21 @@
     if (!length)
         return QString("");
 
-    unsigned char buf[length];
+    unsigned char buf[length+1];
+    memset(buf, 0, length+1);
     memcpy(buf, src, length);
 
     if ((buf[0] <= 0x10) || (buf[0] >= 0x20))
     {
         // Strip formatting characters
         for (uint p = 0; p < length; p++)
-        {
-            if ((buf[p] >= 0x80) && (buf[p] <= 0x9F))
-                memmove(buf + p, buf + p + 1, --length - p);
+	{
+	    if ((buf[p] >= 0x80) && (buf[p] <= 0x9F)){
+	       if (p < length - 1){
+		   memmove(buf + p, buf + p + 1, --length - p);
+	       } 
+	       length--;
+	    }
         }
 
         if (buf[0] >= 0x20)
@@ -30,9 +35,12 @@
         }
         else if ((buf[0] >= 0x01) && (buf[0] <= 0x0B))
         {
-            QString coding = "ISO8859-" + QString::number(4 + buf[0]);
+	    QString coding = "ISO8859-" + QString::number(4 + int(buf[0]));
             QTextCodec *codec = QTextCodec::codecForName(coding);
-            result = codec->toUnicode((const char*)buf + 1, length - 1);
+	    if (codec && length > 1)
+		result = codec->toUnicode((const char*)buf + 1, length - 1);
+	    else 
+	        result = "N/A";
         }
         else if (buf[0] == 0x10)
         {
@@ -41,17 +49,26 @@
             // to indicate that the remaining data of the text field is
             // coded using the character code table specified by
             // ISO Standard 8859, parts 1 to 9
+            uint code = 1;
+	    uint16_t co=0;
 
-            uint code = 1;
-            swab(buf + 1, &code, 2);
-            QString coding = "ISO8859-" + QString::number(code);
-            QTextCodec *codec = QTextCodec::codecForName(coding);
-            result = codec->toUnicode((const char*)buf + 3, length - 3);
+	    co = buf[0] << 8 | buf[1];
+	    code = uint(co);
+	    QString coding = "ISO8859-" + QString::number(code);
+	    QTextCodec *codec = QTextCodec::codecForName(coding);
+	    if (codec && length > 3){
+		result = codec->toUnicode((const char*)buf + 3, length - 3);
+	    } else {
+		result = "N/A";
+	    }
         }
         else
         {
             // Unknown/invalid encoding - assume local8Bit
-            result = QString::fromLocal8Bit((const char*)buf + 1, length - 1);
+	    if (length > 1)
+		result = QString::fromLocal8Bit((const char*)buf + 1, length - 1);
+	    else 
+		result = "N/A";
         }
     }
     else
@@ -62,7 +79,6 @@
                 "Multi-byte coded text - not supported!");
         result = "N/A";
     }
-
     return result;
 }


-- 
/--------------------------------------------------------------------\
| Dr. Marcus O.C. Metzler        |                                   |
| mocm at metzlerbros.de            | http://www.metzlerbros.de/        |
\--------------------------------------------------------------------/
 |>>>             Quis custodiet ipsos custodes                 <<<|