commit 880a4e8512343462353f69ddecb63ae1748b9902
Author: Peter Penz <peter.penz19@gmail.com>
Date:   Sat Aug 20 19:14:28 2011 +0200

    Don't hang when determining MIME type of corrupted files
    
    The patch has been provided by Miroslav Ľos.
    
    BUG: 280446

diff --git a/kdecore/services/kmimetype.cpp b/kdecore/services/kmimetype.cpp
index 955bf62..a4631f2 100644
--- a/kdecore/services/kmimetype.cpp
+++ b/kdecore/services/kmimetype.cpp
@@ -218,7 +218,7 @@ KMimeType::Ptr KMimeType::findByUrlHelper( const KUrl& _url, mode_t mode,
     }
 
     if ( device && !device->isOpen() ) {
-        if ( !device->open(QIODevice::ReadOnly) ) {
+        if ( !device->open(QIODevice::ReadOnly|QIODevice::Unbuffered) ) {
             device = 0;
         }
     }
@@ -383,7 +383,7 @@ KMimeType::Ptr KMimeType::findByFileContent( const QString &fileName, int *accur
             *accuracy = 100;
         return mimeFromMode;
     }
-    if (!device.open(QIODevice::ReadOnly)) {
+    if (!device.open(QIODevice::ReadOnly|QIODevice::Unbuffered)) {
         if (accuracy)
             *accuracy = 0;
         return KMimeType::defaultMimeTypePtr();
diff --git a/kdecore/services/kmimetyperepository.cpp b/kdecore/services/kmimetyperepository.cpp
index 6ff3d16..7a69005 100644
--- a/kdecore/services/kmimetyperepository.cpp
+++ b/kdecore/services/kmimetyperepository.cpp
@@ -234,6 +234,14 @@ KMimeType::Ptr KMimeTypeRepository::findFromContent(QIODevice* device, int* accu
             *accuracy = 100;
         return findMimeTypeByName(QLatin1String("application/x-zerosize"));
     }
+    if (beginning.isEmpty()) {
+        // check if we can really read the data; also provide enough data for most rules
+        const qint64 dataNeeded = qMin(deviceSize, (qint64) 2048);
+        beginning.resize(dataNeeded);
+        if (!device->seek(0) || device->read(beginning.data(), dataNeeded) == -1) {
+            return defaultMimeTypePtr(); // don't bother detecting unreadable file
+        }
+    }
 
     m_mutex.lockForWrite();
     if (!m_magicFilesParsed) {