avoid possible memory overrun in strchr()

* add a loop to look for newlines that takes the known
  file size into account so we don't risk accessing
  outside the valid mapped area.
* also, add a log warning (acting as explanation for
  this-should-not-happen handling code).

2 files changed, 18 insertions, 4 deletions

diff --git a/vespalog/src/vespa/log/control-file.cpp b/vespalog/src/vespa/log/control-file.cpp
index 70833847905..391a2522538 100644
--- a/vespalog/src/vespa/log/control-file.cpp
+++ b/vespalog/src/vespa/log/control-file.cpp
@@ -144,6 +144,18 @@ ControlFile::pageAlign(unsigned int len)
 }
 
 char *
+ControlFile::nextNewline(char *addr)
+{
+    if (addr < _mapBase) return NULL;
+    char *end = _mapBase + _fileSize;
+    while (addr < end) {
+        if (*addr == '\n') return addr;
+        ++addr;
+    }
+    return NULL;
+}
+
+char *
 ControlFile::alignLevels(char *addr)
 {
     unsigned long x = reinterpret_cast<unsigned long>(addr);
@@ -424,12 +436,13 @@ Component *
 ComponentIterator::next()
 {
     Component *ret = NULL;
-    if (_next && _cf->insideFile(_next) && _next[0]) {
-        char *nn = strchr(_next, '\n');
-        if (nn && _cf->insideFile(nn)) {
+    if (_next) {
+        char *nn = _cf->nextNewline(_next);
+        if (nn) {
             ret = new Component(_next);
             _next = ++nn;
             if (nn != ret->endPointer()) {
+                LOG(warning, "mismatch between component size and line size, aborting ComponentIterator loop");
                 delete ret;
                 ret = NULL;
                 _next = NULL;
diff --git a/vespalog/src/vespa/log/control-file.h b/vespalog/src/vespa/log/control-file.h
index 886f38791ba..f3d42251441 100644
--- a/vespalog/src/vespa/log/control-file.h
+++ b/vespalog/src/vespa/log/control-file.h
@@ -35,6 +35,8 @@ private:
     int _mappedSize;
     char *_firstComponent;
 
+    char *nextNewline(char *p);
+
     static const int _maxMapSize = 200000;
     static const int _maxPrefix = 64;
 
@@ -57,7 +59,6 @@ public:
     ~ControlFile();
     unsigned int *getLevels(const char *name);
     void ensureComponent(const char *pattern);
-    bool insideFile(char *p) { return (p >= _mapBase) && (p < _mapBase + _fileSize); }
 
     static unsigned int *defaultLevels();