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ladybird/Kernel/FileSystem/ProcFS.h
Tom c8d9f1b9c9 Kernel: Make copy_to/from_user safe and remove unnecessary checks 
Since the CPU already does almost all necessary validation steps
for us, we don't really need to attempt to do this. Doing it
ourselves doesn't really work very reliably, because we'd have to
account for other processors modifying virtual memory, and we'd
have to account for e.g. pages not being able to be allocated
due to insufficient resources.

So change the copy_to/from_user (and associated helper functions)
to use the new safe_memcpy, which will return whether it succeeded
or not. The only manual validation step needed (which the CPU
can't perform for us) is making sure the pointers provided by user
mode aren't pointing to kernel mappings.

To make it easier to read/write from/to either kernel or user mode
data add the UserOrKernelBuffer helper class, which will internally
either use copy_from/to_user or directly memcpy, or pass the data
through directly using a temporary buffer on the stack.

Last but not least we need to keep syscall params trivial as we
need to copy them from/to user mode using copy_from/to_user.
2020-09-13 21:19:15 +02:00

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/HashMap.h>
#include <AK/Types.h>
#include <Kernel/FileSystem/FileSystem.h>
#include <Kernel/FileSystem/Inode.h>
#include <Kernel/KBuffer.h>
#include <Kernel/Lock.h>
namespace Kernel {
class Process;
class ProcFSInode;
class ProcFS final : public FS {
friend class ProcFSInode;
public:
virtual ~ProcFS() override;
static NonnullRefPtr<ProcFS> create();
virtual bool initialize() override;
virtual const char* class_name() const override;
virtual NonnullRefPtr<Inode> root_inode() const override;
static void add_sys_bool(String&&, Lockable<bool>&, Function<void()>&& notify_callback = nullptr);
static void add_sys_string(String&&, Lockable<String>&, Function<void()>&& notify_callback = nullptr);
private:
ProcFS();
struct ProcFSDirectoryEntry {
ProcFSDirectoryEntry() { }
ProcFSDirectoryEntry(const char* a_name, unsigned a_proc_file_type, bool a_supervisor_only, Function<Optional<KBuffer>(InodeIdentifier)>&& a_read_callback = nullptr, Function<ssize_t(InodeIdentifier, const UserOrKernelBuffer&, size_t)>&& a_write_callback = nullptr, RefPtr<ProcFSInode>&& a_inode = nullptr)
: name(a_name)
, proc_file_type(a_proc_file_type)
, supervisor_only(a_supervisor_only)
, read_callback(move(a_read_callback))
, write_callback(move(a_write_callback))
, inode(move(a_inode))
{
}
const char* name { nullptr };
unsigned proc_file_type { 0 };
bool supervisor_only { false };
Function<Optional<KBuffer>(InodeIdentifier)> read_callback;
Function<ssize_t(InodeIdentifier, const UserOrKernelBuffer&, size_t)> write_callback;
RefPtr<ProcFSInode> inode;
InodeIdentifier identifier(unsigned fsid) const;
};
RefPtr<Inode> get_inode(InodeIdentifier) const;
ProcFSDirectoryEntry* get_directory_entry(InodeIdentifier) const;
Vector<ProcFSDirectoryEntry> m_entries;
mutable Lock m_inodes_lock;
mutable HashMap<unsigned, ProcFSInode*> m_inodes;
RefPtr<ProcFSInode> m_root_inode;
};
class ProcFSInode final : public Inode {
friend class ProcFS;
public:
virtual ~ProcFSInode() override;
private:
// ^Inode
virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer& buffer, FileDescription*) const override;
virtual InodeMetadata metadata() const override;
virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override;
virtual RefPtr<Inode> lookup(StringView name) override;
virtual void flush_metadata() override;
virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer& buffer, FileDescription*) override;
virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
virtual KResult remove_child(const StringView& name) override;
virtual KResultOr<size_t> directory_entry_count() const override;
virtual KResult chmod(mode_t) override;
virtual KResult chown(uid_t, gid_t) override;
virtual KResultOr<NonnullRefPtr<Custody>> resolve_as_link(Custody& base, RefPtr<Custody>* out_parent = nullptr, int options = 0, int symlink_recursion_level = 0) const override;
ProcFS& fs() { return static_cast<ProcFS&>(Inode::fs()); }
const ProcFS& fs() const { return static_cast<const ProcFS&>(Inode::fs()); }
ProcFSInode(ProcFS&, unsigned index);
};
class ProcFSProxyInode final : public Inode {
friend class ProcFSInode;
public:
virtual ~ProcFSProxyInode() override;
private:
// ^Inode
virtual ssize_t read_bytes(off_t, ssize_t, UserOrKernelBuffer&, FileDescription*) const override { ASSERT_NOT_REACHED(); }
virtual InodeMetadata metadata() const override;
virtual KResult traverse_as_directory(Function<bool(const FS::DirectoryEntryView&)>) const override { ASSERT_NOT_REACHED(); }
virtual RefPtr<Inode> lookup(StringView name) override;
virtual void flush_metadata() override {};
virtual ssize_t write_bytes(off_t, ssize_t, const UserOrKernelBuffer&, FileDescription*) override { ASSERT_NOT_REACHED(); }
virtual KResultOr<NonnullRefPtr<Inode>> create_child(const String& name, mode_t, dev_t, uid_t, gid_t) override;
virtual KResult add_child(Inode&, const StringView& name, mode_t) override;
virtual KResult remove_child(const StringView& name) override;
virtual KResultOr<size_t> directory_entry_count() const override;
virtual KResult chmod(mode_t) override { return KResult(-EINVAL); }
virtual KResult chown(uid_t, gid_t) override { return KResult(-EINVAL); }
virtual KResultOr<NonnullRefPtr<Custody>> resolve_as_link(Custody&, RefPtr<Custody>*, int, int) const override { ASSERT_NOT_REACHED(); }
virtual FileDescription* preopen_fd() override { return m_fd; }
ProcFS& fs() { return static_cast<ProcFS&>(Inode::fs()); }
const ProcFS& fs() const { return static_cast<const ProcFS&>(Inode::fs()); }
ProcFSProxyInode(ProcFS&, FileDescription&);
static NonnullRefPtr<ProcFSProxyInode> create(ProcFS& fs, FileDescription& fd)
{
return adopt(*new ProcFSProxyInode(fs, fd));
}
NonnullRefPtr<FileDescription> m_fd;
};
}
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