Kernel: Improve ProcFS behavior in low memory conditions

When ProcFS could no longer allocate KBuffer objects to serve calls to
read, it would just return 0, indicating EOF. This then triggered
parsing errors because code assumed it read the file.

Because read isn't supposed to return ENOMEM, change ProcFS to populate
the file data upon file open or seek to the beginning. This also means
that calls to open can now return ENOMEM if needed. This allows the
caller to either be able to successfully open the file and read it, or
fail to open it in the first place.

1 files changed, 5 insertions, 1 deletions

diff --git a/Kernel/Syscalls/watch_file.cpp b/Kernel/Syscalls/watch_file.cpp
index caf8299528..2f6194bc7a 100644
--- a/Kernel/Syscalls/watch_file.cpp
+++ b/Kernel/Syscalls/watch_file.cpp
@@ -52,7 +52,11 @@ int Process::sys$watch_file(Userspace<const char*> user_path, size_t path_length
     if (fd < 0)
         return fd;
 
-    m_fds[fd].set(FileDescription::create(*InodeWatcher::create(inode)));
+    auto description = FileDescription::create(*InodeWatcher::create(inode));
+    if (description.is_error())
+        return description.error();
+
+    m_fds[fd].set(description.release_value());
     m_fds[fd].description()->set_readable(true);
     return fd;
 }