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lib/vfs: improve memory safety at ram file system
Reference count files to prevent dangling handles. Catch out-of-memory conditions and throw NO_SPACE. Issue #1751
This commit is contained in:
Emery Hemingway
Christian Helmuth
parent
82a7799638
commit
58632ab8b5
@ -31,6 +31,8 @@ namespace Vfs_ram {
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enum { MAX_NAME_LEN = 128 };
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typedef Genode::Allocator::Out_of_memory Out_of_memory;
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/**
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* Return base-name portion of null-terminated path string
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*/
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@ -56,14 +58,12 @@ class Vfs_ram::Node : public Genode::Avl_node<Node>, public Genode::Lock
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char _name[MAX_NAME_LEN];
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unsigned long const _inode;
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/**
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* Generate unique inode number
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*
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* XXX: these inodes could clash with other VFS plugins
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*/
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static unsigned long _unique_inode()
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static unsigned _unique_inode()
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{
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static unsigned long inode_count;
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return ++inode_count;
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@ -71,13 +71,13 @@ class Vfs_ram::Node : public Genode::Avl_node<Node>, public Genode::Lock
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public:
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unsigned inode;
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Node(char const *node_name)
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: _inode(_unique_inode()) { name(node_name); }
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: inode(_unique_inode()) { name(node_name); }
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virtual ~Node() { }
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unsigned long inode() const { return _inode; }
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char const *name() { return _name; }
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void name(char const *name) { strncpy(_name, name, MAX_NAME_LEN); }
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@ -144,14 +144,28 @@ class Vfs_ram::File : public Vfs_ram::Node
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typedef ::File_system::Chunk_index<64, Chunk_level_1> Chunk_level_0;
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Chunk_level_0 _chunk;
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file_size _length = 0;
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file_size _length = 0;
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int _open_handles = 0;
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public:
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File(char const *name, Allocator &alloc)
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: Node(name), _chunk(alloc, 0) { }
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/**
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* Increment reference counter
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*/
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void open() { ++_open_handles; }
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bool close_but_keep()
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{
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if (--_open_handles < 0) {
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inode = 0;
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return false;
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}
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return true;
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}
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size_t read(char *dst, size_t len, file_size seek_offset)
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{
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file_size const chunk_used_size = _chunk.used_size();
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@ -194,7 +208,8 @@ class Vfs_ram::File : public Vfs_ram::Node
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if (seek_offset + len >= Chunk_level_0::SIZE)
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len = Chunk_level_0::SIZE - (seek_offset + len);
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_chunk.write(src, len, (size_t)seek_offset);
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try { _chunk.write(src, len, (size_t)seek_offset); }
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catch (Out_of_memory) { return 0; }
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/*
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* Keep track of file length. We cannot use 'chunk.used_size()'
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@ -250,18 +265,25 @@ class Vfs_ram::Directory : public Vfs_ram::Node
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{
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private:
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Avl_tree<Node> _entries;
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file_size _count = 0;
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Avl_tree<Node> _entries;
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file_size _count = 0;
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public:
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Directory(char const *name) : Node(name) { }
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Directory(char const *name)
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: Node(name) { }
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~Directory()
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void empty(Allocator &alloc)
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{
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while (Node *node = _entries.first()) {
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_entries.remove(node);
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destroy(env()->heap(), node);
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if (File *file = dynamic_cast<File*>(node)) {
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if (file->close_but_keep())
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continue;
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} else if (Directory *dir = dynamic_cast<Directory*>(node)) {
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dir->empty(alloc);
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}
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destroy(alloc, node);
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}
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}
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@ -332,7 +354,9 @@ class Vfs::Ram_file_system : public Vfs::File_system
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int status_flags,
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Vfs_ram::File &node)
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: Vfs_handle(fs, fs, alloc, status_flags), file(node)
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{ }
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{
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file.open();
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}
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};
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Genode::Allocator &_alloc;
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@ -382,11 +406,28 @@ class Vfs::Ram_file_system : public Vfs::File_system
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return 0;
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}
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void remove(Vfs_ram::Node *node)
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{
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using namespace Vfs_ram;
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if (File *file = dynamic_cast<File*>(node)) {
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if (file->close_but_keep())
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return;
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} else if (Directory *dir = dynamic_cast<Directory*>(node)) {
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dir->empty(_alloc);
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}
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destroy(_alloc, node);
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}
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public:
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Ram_file_system(Xml_node config)
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: _alloc(*env()->heap()) { }
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~Ram_file_system() { _root.empty(_alloc); }
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/*********************************
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** Directory service interface **
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*********************************/
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@ -430,11 +471,15 @@ class Vfs::Ram_file_system : public Vfs::File_system
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if (parent->child(name)) return MKDIR_ERR_EXISTS;
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parent->adopt(new (_alloc) Directory(name));
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try { parent->adopt(new (_alloc) Directory(name)); }
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catch (Out_of_memory) { return MKDIR_ERR_NO_SPACE; }
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return MKDIR_OK;
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}
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Open_result open(char const *path, unsigned mode, Vfs_handle **handle, Genode::Allocator &alloc) override
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Open_result open(char const *path, unsigned mode,
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Vfs_handle **handle,
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Allocator &alloc) override
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{
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using namespace Vfs_ram;
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@ -451,7 +496,8 @@ class Vfs::Ram_file_system : public Vfs::File_system
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if (strlen(name) >= MAX_NAME_LEN)
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return OPEN_ERR_NAME_TOO_LONG;
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file = new (_alloc) File(name, _alloc);
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try { file = new (_alloc) File(name, _alloc); }
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catch (Out_of_memory) { return OPEN_ERR_NO_SPACE; }
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parent->adopt(file);
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} else {
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Node *node = lookup(path);
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@ -471,7 +517,8 @@ class Vfs::Ram_file_system : public Vfs::File_system
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static_cast<Ram_vfs_handle *>(vfs_handle);
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if (ram_handle) {
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destroy(_alloc, &ram_handle->file);
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if (!ram_handle->file.close_but_keep())
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destroy(_alloc, &ram_handle->file);
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destroy(vfs_handle->alloc(), ram_handle);
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}
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}
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@ -484,7 +531,7 @@ class Vfs::Ram_file_system : public Vfs::File_system
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if (!node) return STAT_ERR_NO_ENTRY;
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Node::Guard guard(node);
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stat.inode = node->inode();
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stat.inode = node->inode;
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stat.size = node->length();
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File *file = dynamic_cast<File *>(node);
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@ -547,7 +594,9 @@ class Vfs::Ram_file_system : public Vfs::File_system
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if (strlen(name) >= MAX_NAME_LEN)
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return SYMLINK_ERR_NAME_TOO_LONG;
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link = new (_alloc) Symlink(name);
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try { link = new (_alloc) Symlink(name); }
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catch (Out_of_memory) { return SYMLINK_ERR_NO_SPACE; }
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link->lock();
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parent->adopt(link);
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}
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@ -562,10 +611,8 @@ class Vfs::Ram_file_system : public Vfs::File_system
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file_size buf_size, file_size &out_len) override
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{
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using namespace Vfs_ram;
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Directory *parent = lookup_parent(path);
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if (!parent)
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return READLINK_ERR_NO_ENTRY;
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if (!parent) return READLINK_ERR_NO_ENTRY;
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Node::Guard parent_guard(parent);
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Node *node = parent->child(basename(path));
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@ -616,7 +663,7 @@ class Vfs::Ram_file_system : public Vfs::File_system
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return RENAME_ERR_NO_PERM;
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to_dir->release(to_node);
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destroy(_alloc, to_node);
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remove(to_node);
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}
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from_dir->release(from_node);
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@ -639,7 +686,7 @@ class Vfs::Ram_file_system : public Vfs::File_system
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node->lock();
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parent->release(node);
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destroy(_alloc, node);
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remove(node);
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return UNLINK_OK;
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}
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@ -687,7 +734,7 @@ class Vfs::Ram_file_system : public Vfs::File_system
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char const *buf, file_size len,
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Vfs::file_size &out) override
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{
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if (!(vfs_handle->status_flags() & (OPEN_MODE_WRONLY|OPEN_MODE_RDWR)))
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if ((vfs_handle->status_flags() & OPEN_MODE_ACCMODE) == OPEN_MODE_RDONLY)
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return WRITE_ERR_INVALID;
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Ram_vfs_handle const *handle =
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@ -717,14 +764,16 @@ class Vfs::Ram_file_system : public Vfs::File_system
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Ftruncate_result ftruncate(Vfs_handle *vfs_handle, file_size len) override
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{
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if (!(vfs_handle->status_flags() & (OPEN_MODE_WRONLY|OPEN_MODE_RDWR)))
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if ((vfs_handle->status_flags() & OPEN_MODE_ACCMODE) == OPEN_MODE_RDONLY)
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return FTRUNCATE_ERR_NO_PERM;
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Ram_vfs_handle const *handle =
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static_cast<Ram_vfs_handle *>(vfs_handle);
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Vfs_ram::Node::Guard guard(&handle->file);
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handle->file.truncate(len);
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try { handle->file.truncate(len); }
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catch (Vfs_ram::Out_of_memory) { return FTRUNCATE_ERR_NO_SPACE; }
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return FTRUNCATE_OK;
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}
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