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https://github.com/SerenityOS/serenity
synced 2024-10-14 20:03:29 +00:00
Kernel: Make Inode::lookup() return a RefPtr<Inode>
Previously this API would return an InodeIdentifier, which meant that there was a race in path resolution where an inode could be unlinked in between finding the InodeIdentifier for a path component, and actually resolving that to an Inode object. Attaching a test that would quickly trip an assertion before. Test: Kernel/path-resolution-race.cpp
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@ -169,17 +169,17 @@ size_t DevPtsFSInode::directory_entry_count() const
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return 2 + ptys->size();
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}
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InodeIdentifier DevPtsFSInode::lookup(StringView name)
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RefPtr<Inode> DevPtsFSInode::lookup(StringView name)
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{
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ASSERT(identifier().index() == 1);
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if (name == "." || name == "..")
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return identifier();
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return fs().get_inode(identifier());
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bool ok;
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unsigned pty_index = name.to_uint(ok);
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if (ok && ptys->contains(pty_index)) {
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return { fsid(), pty_index_to_inode_index(pty_index) };
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return fs().get_inode({ fsid(), pty_index_to_inode_index(pty_index) });
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}
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return {};
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@ -67,7 +67,7 @@ private:
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virtual ssize_t read_bytes(off_t, ssize_t, u8* buffer, FileDescription*) const override;
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virtual InodeMetadata metadata() const override;
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virtual bool traverse_as_directory(Function<bool(const FS::DirectoryEntry&)>) const override;
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virtual InodeIdentifier lookup(StringView name) override;
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virtual RefPtr<Inode> lookup(StringView name) override;
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virtual void flush_metadata() override;
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virtual ssize_t write_bytes(off_t, ssize_t, const u8* buffer, FileDescription*) override;
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virtual KResult add_child(InodeIdentifier child_id, const StringView& name, mode_t) override;
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@ -1493,14 +1493,14 @@ void Ext2FSInode::populate_lookup_cache() const
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m_lookup_cache = move(children);
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}
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InodeIdentifier Ext2FSInode::lookup(StringView name)
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RefPtr<Inode> Ext2FSInode::lookup(StringView name)
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{
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ASSERT(is_directory());
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populate_lookup_cache();
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LOCKER(m_lock);
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auto it = m_lookup_cache.find(name.hash(), [&](auto& entry) { return entry.key == name; });
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if (it != m_lookup_cache.end())
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return { fsid(), (*it).value };
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return fs().get_inode({ fsid(), (*it).value });
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return {};
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}
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@ -57,7 +57,7 @@ private:
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virtual ssize_t read_bytes(off_t, ssize_t, u8* buffer, FileDescription*) const override;
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virtual InodeMetadata metadata() const override;
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virtual bool traverse_as_directory(Function<bool(const FS::DirectoryEntry&)>) const override;
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virtual InodeIdentifier lookup(StringView name) override;
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virtual RefPtr<Inode> lookup(StringView name) override;
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virtual void flush_metadata() override;
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virtual ssize_t write_bytes(off_t, ssize_t, const u8* data, FileDescription*) override;
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virtual KResult add_child(InodeIdentifier child_id, const StringView& name, mode_t) override;
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@ -72,7 +72,7 @@ public:
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virtual ssize_t read_bytes(off_t, ssize_t, u8* buffer, FileDescription*) const = 0;
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virtual bool traverse_as_directory(Function<bool(const FS::DirectoryEntry&)>) const = 0;
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virtual InodeIdentifier lookup(StringView name) = 0;
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virtual RefPtr<Inode> lookup(StringView name) = 0;
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virtual ssize_t write_bytes(off_t, ssize_t, const u8* data, FileDescription*) = 0;
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virtual KResult add_child(InodeIdentifier child_id, const StringView& name, mode_t) = 0;
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virtual KResult remove_child(const StringView& name) = 0;
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@ -1298,13 +1298,13 @@ bool ProcFSInode::traverse_as_directory(Function<bool(const FS::DirectoryEntry&)
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return true;
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}
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InodeIdentifier ProcFSInode::lookup(StringView name)
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RefPtr<Inode> ProcFSInode::lookup(StringView name)
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{
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ASSERT(is_directory());
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if (name == ".")
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return identifier();
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return fs().get_inode(identifier());
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if (name == "..")
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return to_parent_id(identifier());
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return fs().get_inode(to_parent_id(identifier()));
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auto proc_file_type = to_proc_file_type(identifier());
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@ -1314,7 +1314,7 @@ InodeIdentifier ProcFSInode::lookup(StringView name)
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continue;
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if (entry.proc_file_type > __FI_Root_Start && entry.proc_file_type < __FI_Root_End) {
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if (name == entry.name) {
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return to_identifier(fsid(), PDI_Root, 0, (ProcFileType)entry.proc_file_type);
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return fs().get_inode(to_identifier(fsid(), PDI_Root, 0, (ProcFileType)entry.proc_file_type));
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}
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}
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}
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@ -1327,7 +1327,7 @@ InodeIdentifier ProcFSInode::lookup(StringView name)
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process_exists = Process::from_pid(name_as_number);
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}
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if (process_exists)
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return to_identifier(fsid(), PDI_Root, name_as_number, FI_PID);
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return fs().get_inode(to_identifier(fsid(), PDI_Root, name_as_number, FI_PID));
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}
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return {};
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}
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@ -1336,22 +1336,22 @@ InodeIdentifier ProcFSInode::lookup(StringView name)
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for (int i = 1; i < sys_variables().size(); ++i) {
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auto& variable = sys_variables()[i];
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if (name == variable.name)
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return sys_var_to_identifier(fsid(), i);
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return fs().get_inode(sys_var_to_identifier(fsid(), i));
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}
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return {};
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}
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if (proc_file_type == FI_Root_net) {
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if (name == "adapters")
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return to_identifier(fsid(), PDI_Root, 0, FI_Root_net_adapters);
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return fs().get_inode(to_identifier(fsid(), PDI_Root, 0, FI_Root_net_adapters));
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if (name == "arp")
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return to_identifier(fsid(), PDI_Root, 0, FI_Root_net_arp);
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return fs().get_inode(to_identifier(fsid(), PDI_Root, 0, FI_Root_net_arp));
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if (name == "tcp")
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return to_identifier(fsid(), PDI_Root, 0, FI_Root_net_tcp);
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return fs().get_inode(to_identifier(fsid(), PDI_Root, 0, FI_Root_net_tcp));
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if (name == "udp")
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return to_identifier(fsid(), PDI_Root, 0, FI_Root_net_udp);
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return fs().get_inode(to_identifier(fsid(), PDI_Root, 0, FI_Root_net_udp));
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if (name == "local")
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return to_identifier(fsid(), PDI_Root, 0, FI_Root_net_local);
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return fs().get_inode(to_identifier(fsid(), PDI_Root, 0, FI_Root_net_local));
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return {};
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}
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@ -1367,7 +1367,7 @@ InodeIdentifier ProcFSInode::lookup(StringView name)
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if (entry.name == nullptr)
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continue;
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if (name == entry.name) {
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return to_identifier(fsid(), PDI_PID, to_pid(identifier()), (ProcFileType)entry.proc_file_type);
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return fs().get_inode(to_identifier(fsid(), PDI_PID, to_pid(identifier()), (ProcFileType)entry.proc_file_type));
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}
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}
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}
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@ -1385,7 +1385,7 @@ InodeIdentifier ProcFSInode::lookup(StringView name)
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fd_exists = process->file_description(name_as_number);
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}
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if (fd_exists)
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return to_identifier_with_fd(fsid(), to_pid(identifier()), name_as_number);
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return fs().get_inode(to_identifier_with_fd(fsid(), to_pid(identifier()), name_as_number));
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}
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}
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return {};
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@ -1529,7 +1529,7 @@ KResult ProcFSProxyInode::remove_child(const StringView& name)
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return m_fd->inode()->remove_child(name);
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}
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InodeIdentifier ProcFSProxyInode::lookup(StringView name)
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RefPtr<Inode> ProcFSProxyInode::lookup(StringView name)
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{
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if (!m_fd->inode())
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return {};
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@ -99,7 +99,7 @@ private:
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virtual ssize_t read_bytes(off_t, ssize_t, u8* buffer, FileDescription*) const override;
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virtual InodeMetadata metadata() const override;
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virtual bool traverse_as_directory(Function<bool(const FS::DirectoryEntry&)>) const override;
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virtual InodeIdentifier lookup(StringView name) override;
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virtual RefPtr<Inode> lookup(StringView name) override;
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virtual void flush_metadata() override;
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virtual ssize_t write_bytes(off_t, ssize_t, const u8* buffer, FileDescription*) override;
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virtual KResult add_child(InodeIdentifier child_id, const StringView& name, mode_t) override;
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@ -125,7 +125,7 @@ private:
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virtual ssize_t read_bytes(off_t, ssize_t, u8*, FileDescription*) const override { ASSERT_NOT_REACHED(); }
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virtual InodeMetadata metadata() const override;
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virtual bool traverse_as_directory(Function<bool(const FS::DirectoryEntry&)>) const override { ASSERT_NOT_REACHED(); }
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virtual InodeIdentifier lookup(StringView name) override;
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virtual RefPtr<Inode> lookup(StringView name) override;
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virtual void flush_metadata() override {};
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virtual ssize_t write_bytes(off_t, ssize_t, const u8*, FileDescription*) override { ASSERT_NOT_REACHED(); }
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virtual KResult add_child(InodeIdentifier child_id, const StringView& name, mode_t) override;
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@ -233,20 +233,20 @@ ssize_t TmpFSInode::write_bytes(off_t offset, ssize_t size, const u8* buffer, Fi
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return size;
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}
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InodeIdentifier TmpFSInode::lookup(StringView name)
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RefPtr<Inode> TmpFSInode::lookup(StringView name)
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{
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LOCKER(m_lock);
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ASSERT(is_directory());
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if (name == ".")
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return identifier();
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return fs().get_inode(identifier());
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if (name == "..")
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return m_parent;
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return fs().get_inode(m_parent);
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auto it = m_children.find(name);
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if (it == m_children.end())
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return {};
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return it->value.entry.inode;
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return fs().get_inode(it->value.entry.inode);
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}
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size_t TmpFSInode::directory_entry_count() const
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@ -77,7 +77,7 @@ public:
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virtual ssize_t read_bytes(off_t, ssize_t, u8* buffer, FileDescription*) const override;
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virtual InodeMetadata metadata() const override;
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virtual bool traverse_as_directory(Function<bool(const FS::DirectoryEntry&)>) const override;
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virtual InodeIdentifier lookup(StringView name) override;
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virtual RefPtr<Inode> lookup(StringView name) override;
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virtual void flush_metadata() override;
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virtual ssize_t write_bytes(off_t, ssize_t, const u8* buffer, FileDescription*) override;
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virtual KResult add_child(InodeIdentifier child_id, const StringView& name, mode_t) override;
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@ -811,9 +811,8 @@ KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& ba
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}
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// Okay, let's look up this part.
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auto child_id = parent.inode().lookup(part);
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if (!child_id.is_valid()) {
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auto child_inode = parent.inode().lookup(part);
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if (!child_inode) {
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if (out_parent) {
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// ENOENT with a non-null parent custody signals to caller that
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// we found the immediate parent of the file, but the file itself
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@ -824,14 +823,13 @@ KResultOr<NonnullRefPtr<Custody>> VFS::resolve_path(StringView path, Custody& ba
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}
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int mount_flags_for_child = parent.mount_flags();
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// See if there's something mounted on the child; in that case
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// we would need to return the guest inode, not the host inode.
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if (auto mount = find_mount_for_host(child_id)) {
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child_id = mount->guest();
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if (auto mount = find_mount_for_host(child_inode->identifier())) {
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child_inode = get_inode(mount->guest());
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mount_flags_for_child = mount->flags();
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}
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auto child_inode = get_inode(child_id);
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ASSERT(child_inode);
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custody = Custody::create(&parent, part, *child_inode, mount_flags_for_child);
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16
Tests/Kernel/path-resolution-race.cpp
Normal file
16
Tests/Kernel/path-resolution-race.cpp
Normal file
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@ -0,0 +1,16 @@
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#include <unistd.h>
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#include <sys/stat.h>
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int main()
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{
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if (!fork()) {
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for (;;) {
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mkdir("/tmp/x", 0666);
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rmdir("/tmp/x");
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}
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}
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for (;;) {
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chdir("/tmp/x");
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}
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return 0;
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}
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