Add per-task limit for open fd's. Hard-coded at 16 for now.

Kernel/Task.cpp

@@ -746,31 +746,18 @@ int Task::sys$getcwd(char* buffer, size_t size)
 
 int Task::sys$open(const char* path, size_t pathLength)
 {
-    Task::checkSanity("sys$open");
 #ifdef DEBUG_IO
     kprintf("Task::sys$open(): PID=%u, path=%s {%u}\n", m_pid, path, pathLength);
 #endif
-    auto* handle = openFile(String(path, pathLength));
-    if (handle)
-        return handle->fd();
-    return -1;
-}
-
-FileHandle* Task::openFile(String&& path)
-{
-    auto handle = VirtualFileSystem::the().open(move(path), m_cwd.ptr());
-    if (!handle) {
-#ifdef DEBUG_IO
-        kprintf("vfs::open() failed\n");
-#endif
-        return nullptr;
-    }
-    handle->setFD(m_fileHandles.size());
-#ifdef DEBUG_IO
-    kprintf("vfs::open() worked! handle=%p, fd=%d\n", handle.ptr(), handle->fd());
-#endif
-    m_fileHandles.append(move(handle)); // FIXME: allow non-move Vector::append
-    return m_fileHandles.last().ptr();
+    if (m_fileHandles.size() >= m_maxFileHandles)
+        return -EMFILE;
+    auto handle = VirtualFileSystem::the().open(String(path, pathLength), m_cwd.ptr());
+    if (!handle)
+        return -ENOENT; // FIXME: Detailed error.
+    int fd = m_fileHandles.size();
+    handle->setFD(fd);
+    m_fileHandles.append(move(handle));
+    return fd;
 }
 
 int Task::sys$kill(pid_t pid, int sig)

Kernel/Task.h

@@ -124,8 +124,6 @@ private:
 
     Task(String&& name, uid_t, gid_t, pid_t parentPID, RingLevel);
 
-    FileHandle* openFile(String&&);
-
     void allocateLDT();
 
     Task* m_prev { nullptr };
@@ -151,6 +149,7 @@ private:
     dword m_timesScheduled { 0 };
     pid_t m_waitee { -1 };
     int m_fdBlockedOnRead { -1 };
+    size_t m_maxFileHandles { 16 };
 
     RetainPtr<VirtualFileSystem::Node> m_cwd;