Fix deadlock in synthfs read implementation.

Not cool disabling interrupts and then calling out to arbitrary code.

VirtualFileSystem/SyntheticFileSystem.cpp

@@ -194,19 +194,22 @@ bool SyntheticFileSystem::writeInode(InodeIdentifier, const ByteBuffer&)
 
 Unix::ssize_t SyntheticFileSystem::readInodeBytes(InodeIdentifier inode, Unix::off_t offset, Unix::size_t count, byte* buffer, FileDescriptor* handle) const
 {
- InterruptDisabler disabler;
-
  ASSERT(inode.fileSystemID() == id());
 #ifdef SYNTHFS_DEBUG
  kprintf("synthfs: readInode %u\n", inode.index());
 #endif
  ASSERT(offset >= 0);
  ASSERT(buffer);
 
- auto it = m_inodes.find(inode.index());
- if (it == m_inodes.end())
- return false;
- const File& file = *(*it).value;
+ const File* found_file;
+ {
+ InterruptDisabler disabler;
+ auto it = m_inodes.find(inode.index());
+ if (it == m_inodes.end())
+ return false;
+ found_file = (*it).value.ptr();
+ }
+ const File& file = *found_file;
  ByteBuffer generatedData;
  if (file.generator) {
  if (!handle) {