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ladybird/Kernel/FileSystem/VirtualFileSystem.cpp
Liav A e5c7662638 Kernel/VFS: Check matching absolute path when jump to mount guest inode 
We could easily encounter a case where we do the following:

```
mkdir -p /tmp2
mount /dev/hda /tmp2
```

would produce a bug that doing `ls /tmp2/tmp2` will give the contents
on `/dev/hda` ext2 root directory and also on `/tmp2/tmp2/tmp2` and so
on.
To prevent this, we must compare the current custody against each mount
entry's custody to ensure their paths match.
2023-08-05 18:41:01 +02:00

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2022-2023, Liav A. <liavalb@hotmail.co.il>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/AnyOf.h>
#include <AK/GenericLexer.h>
#include <AK/RefPtr.h>
#include <AK/Singleton.h>
#include <AK/StringBuilder.h>
#include <Kernel/API/POSIX/errno.h>
#include <Kernel/Debug.h>
#include <Kernel/Devices/BlockDevice.h>
#include <Kernel/Devices/DeviceManagement.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/FileSystem/FileBackedFileSystem.h>
#include <Kernel/FileSystem/FileSystem.h>
#include <Kernel/FileSystem/OpenFileDescription.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
#include <Kernel/KSyms.h>
#include <Kernel/Library/KLexicalPath.h>
#include <Kernel/Sections.h>
#include <Kernel/Tasks/Process.h>
#include <Kernel/FileSystem/DevPtsFS/FileSystem.h>
#include <Kernel/FileSystem/Ext2FS/FileSystem.h>
#include <Kernel/FileSystem/FATFS/FileSystem.h>
#include <Kernel/FileSystem/ISO9660FS/FileSystem.h>
#include <Kernel/FileSystem/Plan9FS/FileSystem.h>
#include <Kernel/FileSystem/ProcFS/FileSystem.h>
#include <Kernel/FileSystem/RAMFS/FileSystem.h>
#include <Kernel/FileSystem/SysFS/FileSystem.h>
namespace Kernel {
static Singleton<VirtualFileSystem> s_the;
static constexpr int root_mount_flags = 0;
static ErrorOr<void> handle_mount_boolean_flag_as_invalid(Span<u8>, StringView, bool)
{
return EINVAL;
}
static ErrorOr<void> handle_mount_unsigned_integer_flag_as_invalid(Span<u8>, StringView, u64)
{
return EINVAL;
}
static ErrorOr<void> handle_mount_signed_integer_flag_as_invalid(Span<u8>, StringView, i64)
{
return EINVAL;
}
static ErrorOr<void> handle_mount_ascii_string_flag_as_invalid(Span<u8>, StringView, StringView)
{
return EINVAL;
}
static constexpr FileSystemInitializer s_initializers[] = {
{ "proc"sv, "ProcFS"sv, false, false, false, {}, ProcFS::try_create, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
{ "devpts"sv, "DevPtsFS"sv, false, false, false, {}, DevPtsFS::try_create, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
{ "sys"sv, "SysFS"sv, false, false, false, {}, SysFS::try_create, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
{ "ram"sv, "RAMFS"sv, false, false, false, {}, RAMFS::try_create, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
{ "ext2"sv, "Ext2FS"sv, true, true, true, Ext2FS::try_create, {}, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
{ "9p"sv, "Plan9FS"sv, true, true, true, Plan9FS::try_create, {}, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
{ "iso9660"sv, "ISO9660FS"sv, true, true, true, ISO9660FS::try_create, {}, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
{ "fat"sv, "FATFS"sv, true, true, true, FATFS::try_create, {}, handle_mount_boolean_flag_as_invalid, handle_mount_unsigned_integer_flag_as_invalid, handle_mount_signed_integer_flag_as_invalid, handle_mount_ascii_string_flag_as_invalid },
};
ErrorOr<FileSystemInitializer const*> VirtualFileSystem::find_filesystem_type_initializer(StringView fs_type)
{
for (auto& initializer_entry : s_initializers) {
if (fs_type == initializer_entry.short_name || fs_type == initializer_entry.name)
return &initializer_entry;
}
return ENODEV;
}
UNMAP_AFTER_INIT void VirtualFileSystem::initialize()
{
s_the.ensure_instance();
}
VirtualFileSystem& VirtualFileSystem::the()
{
return *s_the;
}
UNMAP_AFTER_INIT VirtualFileSystem::VirtualFileSystem()
{
}
UNMAP_AFTER_INIT VirtualFileSystem::~VirtualFileSystem() = default;
InodeIdentifier VirtualFileSystem::root_inode_id() const
{
VERIFY(m_root_inode);
return m_root_inode->identifier();
}
bool VirtualFileSystem::check_matching_absolute_path_hierarchy(Custody const& first_custody, Custody const& second_custody)
{
// Are both custodies the root mount?
if (!first_custody.parent() && !second_custody.parent())
return true;
if (first_custody.name() != second_custody.name())
return false;
auto const* custody1 = &first_custody;
auto const* custody2 = &second_custody;
while (custody1->parent()) {
if (!custody2->parent())
return false;
if (custody1->parent().ptr() != custody2->parent().ptr())
return false;
custody1 = custody1->parent();
custody2 = custody2->parent();
}
return true;
}
bool VirtualFileSystem::mount_point_exists_at_custody(Custody& mount_point)
{
return m_mounts.with([&](auto& mounts) -> bool {
return any_of(mounts, [&mount_point](auto const& existing_mount) {
return existing_mount.host_custody() && check_matching_absolute_path_hierarchy(*existing_mount.host_custody(), mount_point);
});
});
}
ErrorOr<void> VirtualFileSystem::add_file_system_to_mount_table(FileSystem& file_system, Custody& mount_point, int flags)
{
auto new_mount = TRY(adopt_nonnull_own_or_enomem(new (nothrow) Mount(file_system, &mount_point, flags)));
return m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
auto& mount_point_inode = mount_point.inode();
dbgln("VirtualFileSystem: FileSystemID {}, Mounting {} at inode {} with flags {}",
file_system.fsid(),
file_system.class_name(),
mount_point_inode.identifier(),
flags);
if (mount_point_exists_at_custody(mount_point)) {
dbgln("VirtualFileSystem: Mounting unsuccessful - inode {} is already a mount-point.", mount_point_inode.identifier());
return EBUSY;
}
// Note: Actually add a mount for the filesystem and increment the filesystem mounted count
new_mount->guest_fs().mounted_count({}).with([&](auto& mounted_count) {
mounted_count++;
// When this is the first time this FileSystem is mounted,
// begin managing the FileSystem by adding it to the list of
// managed file systems. This is symmetric with
// VirtualFileSystem::unmount()'s `remove()` calls (which remove
// the FileSystem once it is no longer mounted).
if (mounted_count == 1) {
m_file_systems_list.with([&](auto& fs_list) {
fs_list.append(file_system);
});
}
});
// NOTE: Leak the mount pointer so it can be added to the mount list, but it won't be
// deleted after being added.
mounts.append(*new_mount.leak_ptr());
return {};
});
}
ErrorOr<void> VirtualFileSystem::mount(MountFile& mount_file, OpenFileDescription* source_description, Custody& mount_point, int flags)
{
auto const& file_system_initializer = mount_file.file_system_initializer();
if (!source_description) {
if (file_system_initializer.requires_open_file_description)
return ENOTSUP;
if (!file_system_initializer.create)
return ENOTSUP;
RefPtr<FileSystem> fs;
TRY(mount_file.mount_file_system_specific_data().with_exclusive([&](auto& mount_specific_data) -> ErrorOr<void> {
fs = TRY(file_system_initializer.create(mount_specific_data->bytes()));
return {};
}));
VERIFY(fs);
TRY(fs->initialize());
TRY(add_file_system_to_mount_table(*fs, mount_point, flags));
return {};
}
// NOTE: Although it might be OK to support creating filesystems
// without providing an actual file descriptor to their create() method
// because the caller of this function actually supplied a valid file descriptor,
// this will only make things complicated in the future, so we should block
// this kind of behavior.
if (!file_system_initializer.requires_open_file_description)
return ENOTSUP;
if (file_system_initializer.requires_block_device && !source_description->file().is_block_device())
return ENOTBLK;
if (file_system_initializer.requires_seekable_file && !source_description->file().is_seekable()) {
dbgln("mount: this is not a seekable file");
return ENODEV;
}
// NOTE: If there's an associated file description with the filesystem, we could
// try to first find it from the VirtualFileSystem filesystem list and if it was not found,
// then create it and add it.
VERIFY(file_system_initializer.create_with_fd);
return m_file_backed_file_systems_list.with_exclusive([&](auto& list) -> ErrorOr<void> {
RefPtr<FileSystem> fs;
for (auto& node : list) {
if ((&node.file_description() == source_description) || (&node.file() == &source_description->file())) {
fs = node;
break;
}
}
if (!fs) {
TRY(mount_file.mount_file_system_specific_data().with_exclusive([&](auto& mount_specific_data) -> ErrorOr<void> {
fs = TRY(file_system_initializer.create_with_fd(*source_description, mount_specific_data->bytes()));
return {};
}));
TRY(fs->initialize());
}
TRY(add_file_system_to_mount_table(*fs, mount_point, flags));
list.append(static_cast<FileBackedFileSystem&>(*fs));
return {};
});
}
ErrorOr<void> VirtualFileSystem::bind_mount(Custody& source, Custody& mount_point, int flags)
{
auto new_mount = TRY(adopt_nonnull_own_or_enomem(new (nothrow) Mount(source.inode(), mount_point, flags)));
return m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
auto& inode = mount_point.inode();
dbgln("VirtualFileSystem: Bind-mounting inode {} at inode {}", source.inode().identifier(), inode.identifier());
if (mount_point_exists_at_custody(mount_point)) {
dbgln("VirtualFileSystem: Bind-mounting unsuccessful - inode {} is already a mount-point.",
mount_point.inode().identifier());
return EBUSY;
}
// A bind mount also counts as a normal mount from the perspective of unmount(),
// so we need to keep track of it in order for prepare_to_clear_last_mount() to work properly.
new_mount->guest_fs().mounted_count({}).with([&](auto& count) { count++; });
// NOTE: Leak the mount pointer so it can be added to the mount list, but it won't be
// deleted after being added.
mounts.append(*new_mount.leak_ptr());
return {};
});
}
ErrorOr<void> VirtualFileSystem::remount(Custody& mount_point, int new_flags)
{
dbgln("VirtualFileSystem: Remounting inode {}", mount_point.inode().identifier());
auto* mount = find_mount_for_guest(mount_point.inode().identifier());
if (!mount)
return ENODEV;
mount->set_flags(new_flags);
return {};
}
void VirtualFileSystem::sync_filesystems()
{
Vector<NonnullRefPtr<FileSystem>, 32> file_systems;
m_file_systems_list.with([&](auto const& list) {
for (auto& fs : list)
file_systems.append(fs);
});
for (auto& fs : file_systems)
fs->flush_writes();
}
void VirtualFileSystem::lock_all_filesystems()
{
Vector<NonnullRefPtr<FileSystem>, 32> file_systems;
m_file_systems_list.with([&](auto const& list) {
for (auto& fs : list)
file_systems.append(fs);
});
for (auto& fs : file_systems)
fs->m_lock.lock();
}
ErrorOr<void> VirtualFileSystem::unmount(Custody& mountpoint_custody)
{
auto& guest_inode = mountpoint_custody.inode();
auto custody_path = TRY(mountpoint_custody.try_serialize_absolute_path());
return unmount(guest_inode, custody_path->view());
}
ErrorOr<void> VirtualFileSystem::unmount(Inode& guest_inode, StringView custody_path)
{
return m_file_backed_file_systems_list.with_exclusive([&](auto& file_backed_fs_list) -> ErrorOr<void> {
TRY(m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
for (auto& mount : mounts) {
if (&mount.guest() != &guest_inode)
continue;
auto mountpoint_path = TRY(mount.absolute_path());
if (custody_path != mountpoint_path->view())
continue;
NonnullRefPtr<FileSystem> fs = mount.guest_fs();
TRY(fs->prepare_to_unmount(mount.guest()));
fs->mounted_count({}).with([&](auto& mounted_count) {
VERIFY(mounted_count > 0);
if (mounted_count == 1) {
dbgln("VirtualFileSystem: Unmounting file system {} for the last time...", fs->fsid());
m_file_systems_list.with([&](auto& list) {
list.remove(*fs);
});
if (fs->is_file_backed()) {
dbgln("VirtualFileSystem: Unmounting file backed file system {} for the last time...", fs->fsid());
auto& file_backed_fs = static_cast<FileBackedFileSystem&>(*fs);
file_backed_fs_list.remove(file_backed_fs);
}
} else {
mounted_count--;
}
});
dbgln("VirtualFileSystem: Unmounting file system {}...", fs->fsid());
mount.m_vfs_list_node.remove();
// NOTE: This is balanced by a `new` statement that is happening in various places before inserting the Mount object to the list.
delete &mount;
return {};
}
dbgln("VirtualFileSystem: Nothing mounted on inode {}", guest_inode.identifier());
return ENODEV;
}));
return {};
});
}
ErrorOr<void> VirtualFileSystem::mount_root(FileSystem& fs)
{
if (m_root_inode) {
dmesgln("VirtualFileSystem: mount_root can't mount another root");
return EEXIST;
}
auto new_mount = TRY(adopt_nonnull_own_or_enomem(new (nothrow) Mount(fs, nullptr, root_mount_flags)));
auto& root_inode = fs.root_inode();
if (!root_inode.is_directory()) {
dmesgln("VirtualFileSystem: root inode ({}) for / is not a directory :(", root_inode.identifier());
return ENOTDIR;
}
m_root_inode = root_inode;
if (fs.is_file_backed()) {
auto pseudo_path = TRY(static_cast<FileBackedFileSystem&>(fs).file_description().pseudo_path());
dmesgln("VirtualFileSystem: mounted root({}) from {} ({})", fs.fsid(), fs.class_name(), pseudo_path);
m_file_backed_file_systems_list.with_exclusive([&](auto& list) {
list.append(static_cast<FileBackedFileSystem&>(fs));
});
} else {
dmesgln("VirtualFileSystem: mounted root({}) from {}", fs.fsid(), fs.class_name());
}
m_file_systems_list.with([&](auto& fs_list) {
fs_list.append(fs);
});
fs.mounted_count({}).with([&](auto& mounted_count) {
mounted_count++;
});
// Note: Actually add a mount for the filesystem and increment the filesystem mounted count
m_mounts.with([&](auto& mounts) {
// NOTE: Leak the mount pointer so it can be added to the mount list, but it won't be
// deleted after being added.
mounts.append(*new_mount.leak_ptr());
});
RefPtr<Custody> new_root_custody = TRY(Custody::try_create(nullptr, ""sv, *m_root_inode, root_mount_flags));
m_root_custody.with([&](auto& root_custody) {
swap(root_custody, new_root_custody);
});
return {};
}
auto VirtualFileSystem::find_mount_for_host_custody(Custody const& current_custody) -> Mount*
{
return m_mounts.with([&](auto& mounts) -> Mount* {
// NOTE: We either search for the root mount or for a mount that has a parent custody!
if (!current_custody.parent()) {
for (auto& mount : mounts) {
if (!mount.host_custody())
return &mount;
}
// NOTE: There must be a root mount entry, so fail if we don't find it.
VERIFY_NOT_REACHED();
} else {
for (auto& mount : mounts) {
if (mount.host_custody() && check_matching_absolute_path_hierarchy(*mount.host_custody(), current_custody)) {
return &mount;
}
}
}
return nullptr;
});
}
auto VirtualFileSystem::find_mount_for_guest(InodeIdentifier id) -> Mount*
{
return m_mounts.with([&](auto& mounts) -> Mount* {
for (auto& mount : mounts) {
if (mount.guest().identifier() == id)
return &mount;
}
return nullptr;
});
}
bool VirtualFileSystem::is_vfs_root(InodeIdentifier inode) const
{
return inode == root_inode_id();
}
ErrorOr<void> VirtualFileSystem::traverse_directory_inode(Inode& dir_inode, Function<ErrorOr<void>(FileSystem::DirectoryEntryView const&)> callback)
{
return dir_inode.traverse_as_directory([&](auto& entry) -> ErrorOr<void> {
TRY(callback({ entry.name, entry.inode, entry.file_type }));
return {};
});
}
ErrorOr<void> VirtualFileSystem::utime(Credentials const& credentials, StringView path, Custody& base, time_t atime, time_t mtime)
{
auto custody = TRY(resolve_path(credentials, path, base));
auto& inode = custody->inode();
if (!credentials.is_superuser() && inode.metadata().uid != credentials.euid())
return EACCES;
if (custody->is_readonly())
return EROFS;
TRY(inode.update_timestamps(UnixDateTime::from_seconds_since_epoch(atime), {}, UnixDateTime::from_seconds_since_epoch(mtime)));
return {};
}
ErrorOr<void> VirtualFileSystem::utimensat(Credentials const& credentials, StringView path, Custody& base, timespec const& atime, timespec const& mtime, int options)
{
auto custody = TRY(resolve_path(credentials, path, base, nullptr, options));
return do_utimens(credentials, custody, atime, mtime);
}
ErrorOr<void> VirtualFileSystem::do_utimens(Credentials const& credentials, Custody& custody, timespec const& atime, timespec const& mtime)
{
auto& inode = custody.inode();
if (!credentials.is_superuser() && inode.metadata().uid != credentials.euid())
return EACCES;
if (custody.is_readonly())
return EROFS;
// NOTE: A standard ext2 inode cannot store nanosecond timestamps.
TRY(inode.update_timestamps(
(atime.tv_nsec != UTIME_OMIT) ? UnixDateTime::from_unix_timespec(atime) : Optional<UnixDateTime> {},
{},
(mtime.tv_nsec != UTIME_OMIT) ? UnixDateTime::from_unix_timespec(mtime) : Optional<UnixDateTime> {}));
return {};
}
ErrorOr<InodeMetadata> VirtualFileSystem::lookup_metadata(Credentials const& credentials, StringView path, Custody& base, int options)
{
auto custody = TRY(resolve_path(credentials, path, base, nullptr, options));
return custody->inode().metadata();
}
ErrorOr<NonnullRefPtr<OpenFileDescription>> VirtualFileSystem::open(Credentials const& credentials, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> owner)
{
return open(Process::current(), credentials, path, options, mode, base, owner);
}
ErrorOr<NonnullRefPtr<OpenFileDescription>> VirtualFileSystem::open(Process const& process, Credentials const& credentials, StringView path, int options, mode_t mode, Custody& base, Optional<UidAndGid> owner)
{
if ((options & O_CREAT) && (options & O_DIRECTORY))
return EINVAL;
RefPtr<Custody> parent_custody;
auto custody_or_error = resolve_path(process, credentials, path, base, &parent_custody, options);
if (custody_or_error.is_error()) {
// NOTE: ENOENT with a non-null parent custody signals us that the immediate parent
// of the file exists, but the file itself does not.
if ((options & O_CREAT) && custody_or_error.error().code() == ENOENT && parent_custody)
return create(process, credentials, path, options, mode, *parent_custody, move(owner));
return custody_or_error.release_error();
}
if ((options & O_CREAT) && (options & O_EXCL))
return EEXIST;
auto& custody = *custody_or_error.value();
auto& inode = custody.inode();
auto metadata = inode.metadata();
if (metadata.is_regular_file() && (custody.mount_flags() & MS_NOREGULAR))
return EACCES;
if ((options & O_DIRECTORY) && !metadata.is_directory())
return ENOTDIR;
bool should_truncate_file = false;
if ((options & O_RDONLY) && !metadata.may_read(credentials))
return EACCES;
if (options & O_WRONLY) {
if (!metadata.may_write(credentials))
return EACCES;
if (metadata.is_directory())
return EISDIR;
should_truncate_file = options & O_TRUNC;
}
if (options & O_EXEC) {
if (!metadata.may_execute(credentials) || (custody.mount_flags() & MS_NOEXEC))
return EACCES;
}
if (metadata.is_fifo()) {
auto fifo = TRY(inode.fifo());
if (options & O_WRONLY) {
auto description = TRY(fifo->open_direction_blocking(FIFO::Direction::Writer));
description->set_rw_mode(options);
description->set_file_flags(options);
description->set_original_inode({}, inode);
return description;
} else if (options & O_RDONLY) {
auto description = TRY(fifo->open_direction_blocking(FIFO::Direction::Reader));
description->set_rw_mode(options);
description->set_file_flags(options);
description->set_original_inode({}, inode);
return description;
}
return EINVAL;
}
if (metadata.is_device()) {
if (custody.mount_flags() & MS_NODEV)
return EACCES;
auto device = DeviceManagement::the().get_device(metadata.major_device, metadata.minor_device);
if (device == nullptr) {
return ENODEV;
}
auto description = TRY(device->open(options));
description->set_original_inode({}, inode);
description->set_original_custody({}, custody);
return description;
}
// Check for read-only FS. Do this after handling devices, but before modifying the inode in any way.
if ((options & O_WRONLY) && custody.is_readonly())
return EROFS;
if (should_truncate_file) {
TRY(inode.truncate(0));
TRY(inode.update_timestamps({}, {}, kgettimeofday()));
}
auto description = TRY(OpenFileDescription::try_create(custody));
description->set_rw_mode(options);
description->set_file_flags(options);
return description;
}
ErrorOr<void> VirtualFileSystem::mknod(Credentials const& credentials, StringView path, mode_t mode, dev_t dev, Custody& base)
{
if (!is_regular_file(mode) && !is_block_device(mode) && !is_character_device(mode) && !is_fifo(mode) && !is_socket(mode))
return EINVAL;
RefPtr<Custody> parent_custody;
auto existing_file_or_error = resolve_path(credentials, path, base, &parent_custody);
if (!existing_file_or_error.is_error())
return EEXIST;
if (!parent_custody)
return ENOENT;
if (existing_file_or_error.error().code() != ENOENT)
return existing_file_or_error.release_error();
auto& parent_inode = parent_custody->inode();
if (!parent_inode.metadata().may_write(credentials))
return EACCES;
if (parent_custody->is_readonly())
return EROFS;
auto basename = KLexicalPath::basename(path);
dbgln_if(VFS_DEBUG, "VirtualFileSystem::mknod: '{}' mode={} dev={} in {}", basename, mode, dev, parent_inode.identifier());
(void)TRY(parent_inode.create_child(basename, mode, dev, credentials.euid(), credentials.egid()));
return {};
}
ErrorOr<NonnullRefPtr<OpenFileDescription>> VirtualFileSystem::create(Credentials const& credentials, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> owner)
{
return create(Process::current(), credentials, path, options, mode, parent_custody, owner);
}
ErrorOr<NonnullRefPtr<OpenFileDescription>> VirtualFileSystem::create(Process const& process, Credentials const& credentials, StringView path, int options, mode_t mode, Custody& parent_custody, Optional<UidAndGid> owner)
{
auto basename = KLexicalPath::basename(path);
auto parent_path = TRY(parent_custody.try_serialize_absolute_path());
auto full_path = TRY(KLexicalPath::try_join(parent_path->view(), basename));
TRY(validate_path_against_process_veil(process, full_path->view(), options));
if (!is_socket(mode) && !is_fifo(mode) && !is_block_device(mode) && !is_character_device(mode)) {
// Turn it into a regular file. (This feels rather hackish.)
mode |= 0100000;
}
auto& parent_inode = parent_custody.inode();
if (!parent_inode.metadata().may_write(credentials))
return EACCES;
if (parent_custody.is_readonly())
return EROFS;
if (is_regular_file(mode) && (parent_custody.mount_flags() & MS_NOREGULAR))
return EACCES;
dbgln_if(VFS_DEBUG, "VirtualFileSystem::create: '{}' in {}", basename, parent_inode.identifier());
auto uid = owner.has_value() ? owner.value().uid : credentials.euid();
auto gid = owner.has_value() ? owner.value().gid : credentials.egid();
auto inode = TRY(parent_inode.create_child(basename, mode, 0, uid, gid));
auto custody = TRY(Custody::try_create(&parent_custody, basename, inode, parent_custody.mount_flags()));
auto description = TRY(OpenFileDescription::try_create(move(custody)));
description->set_rw_mode(options);
description->set_file_flags(options);
return description;
}
ErrorOr<void> VirtualFileSystem::mkdir(Credentials const& credentials, StringView path, mode_t mode, Custody& base)
{
// Unlike in basically every other case, where it's only the last
// path component (the one being created) that is allowed not to
// exist, POSIX allows mkdir'ed path to have trailing slashes.
// Let's handle that case by trimming any trailing slashes.
path = path.trim("/"sv, TrimMode::Right);
if (path.is_empty()) {
// NOTE: This means the path was a series of slashes, which resolves to "/".
path = "/"sv;
}
RefPtr<Custody> parent_custody;
// FIXME: The errors returned by resolve_path_without_veil can leak information about paths that are not unveiled,
// e.g. when the error is EACCESS or similar.
auto result = resolve_path_without_veil(credentials, path, base, &parent_custody);
if (!result.is_error())
return EEXIST;
else if (!parent_custody)
return result.release_error();
// NOTE: If resolve_path fails with a non-null parent custody, the error should be ENOENT.
VERIFY(result.error().code() == ENOENT);
TRY(validate_path_against_process_veil(*parent_custody, O_CREAT));
auto& parent_inode = parent_custody->inode();
if (!parent_inode.metadata().may_write(credentials))
return EACCES;
if (parent_custody->is_readonly())
return EROFS;
auto basename = KLexicalPath::basename(path);
dbgln_if(VFS_DEBUG, "VirtualFileSystem::mkdir: '{}' in {}", basename, parent_inode.identifier());
(void)TRY(parent_inode.create_child(basename, S_IFDIR | mode, 0, credentials.euid(), credentials.egid()));
return {};
}
ErrorOr<void> VirtualFileSystem::access(Credentials const& credentials, StringView path, int mode, Custody& base, AccessFlags access_flags)
{
auto should_follow_symlinks = !has_flag(access_flags, AccessFlags::DoNotFollowSymlinks);
auto custody = TRY(resolve_path(credentials, path, base, nullptr, should_follow_symlinks ? 0 : O_NOFOLLOW_NOERROR));
auto& inode = custody->inode();
auto metadata = inode.metadata();
auto use_effective_ids = has_flag(access_flags, AccessFlags::EffectiveAccess) ? UseEffectiveIDs::Yes : UseEffectiveIDs::No;
if (mode & R_OK) {
if (!metadata.may_read(credentials, use_effective_ids))
return EACCES;
}
if (mode & W_OK) {
if (!metadata.may_write(credentials, use_effective_ids))
return EACCES;
if (custody->is_readonly())
return EROFS;
}
if (mode & X_OK) {
if (!metadata.may_execute(credentials, use_effective_ids))
return EACCES;
}
return {};
}
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::open_directory(Credentials const& credentials, StringView path, Custody& base)
{
auto custody = TRY(resolve_path(credentials, path, base));
auto& inode = custody->inode();
if (!inode.is_directory())
return ENOTDIR;
if (!inode.metadata().may_execute(credentials))
return EACCES;
return custody;
}
ErrorOr<void> VirtualFileSystem::chmod(Credentials const& credentials, Custody& custody, mode_t mode)
{
auto& inode = custody.inode();
if (credentials.euid() != inode.metadata().uid && !credentials.is_superuser())
return EPERM;
if (custody.is_readonly())
return EROFS;
// Only change the permission bits.
mode = (inode.mode() & ~07777u) | (mode & 07777u);
return inode.chmod(mode);
}
ErrorOr<void> VirtualFileSystem::chmod(Credentials const& credentials, StringView path, mode_t mode, Custody& base, int options)
{
auto custody = TRY(resolve_path(credentials, path, base, nullptr, options));
return chmod(credentials, custody, mode);
}
ErrorOr<void> VirtualFileSystem::rename(Credentials const& credentials, Custody& old_base, StringView old_path, Custody& new_base, StringView new_path)
{
RefPtr<Custody> old_parent_custody;
auto old_custody = TRY(resolve_path(credentials, old_path, old_base, &old_parent_custody, O_NOFOLLOW_NOERROR));
auto& old_inode = old_custody->inode();
RefPtr<Custody> new_parent_custody;
auto new_custody_or_error = resolve_path(credentials, new_path, new_base, &new_parent_custody);
if (new_custody_or_error.is_error()) {
if (new_custody_or_error.error().code() != ENOENT || !new_parent_custody)
return new_custody_or_error.release_error();
}
if (!old_parent_custody || !new_parent_custody) {
return EPERM;
}
if (!new_custody_or_error.is_error()) {
auto& new_inode = new_custody_or_error.value()->inode();
if (old_inode.index() != new_inode.index() && old_inode.is_directory() && new_inode.is_directory()) {
size_t child_count = 0;
TRY(new_inode.traverse_as_directory([&child_count](auto&) -> ErrorOr<void> {
++child_count;
return {};
}));
if (child_count > 2)
return ENOTEMPTY;
}
}
auto& old_parent_inode = old_parent_custody->inode();
auto& new_parent_inode = new_parent_custody->inode();
if (&old_parent_inode.fs() != &new_parent_inode.fs())
return EXDEV;
for (auto* new_ancestor = new_parent_custody.ptr(); new_ancestor; new_ancestor = new_ancestor->parent()) {
if (&old_inode == &new_ancestor->inode())
return EDIRINTOSELF;
}
if (!new_parent_inode.metadata().may_write(credentials))
return EACCES;
if (!old_parent_inode.metadata().may_write(credentials))
return EACCES;
if (old_parent_inode.metadata().is_sticky()) {
if (!credentials.is_superuser() && old_parent_inode.metadata().uid != credentials.euid() && old_inode.metadata().uid != credentials.euid())
return EACCES;
}
if (old_parent_custody->is_readonly() || new_parent_custody->is_readonly())
return EROFS;
auto old_basename = KLexicalPath::basename(old_path);
if (old_basename.is_empty() || old_basename == "."sv || old_basename == ".."sv)
return EINVAL;
auto new_basename = KLexicalPath::basename(new_path);
if (new_basename.is_empty() || new_basename == "."sv || new_basename == ".."sv)
return EINVAL;
if (old_basename == new_basename && old_parent_inode.index() == new_parent_inode.index())
return {};
if (!new_custody_or_error.is_error()) {
auto& new_custody = *new_custody_or_error.value();
auto& new_inode = new_custody.inode();
// When the source/dest inodes are the same (in other words,
// when `old_path` and `new_path` are the same), perform a no-op
// and return success.
// Linux (`vfs_rename()`) and OpenBSD (`dorenameat()`) appear to have
// this same no-op behavior.
if (&new_inode == &old_inode)
return {};
if (new_parent_inode.metadata().is_sticky()) {
if (!credentials.is_superuser() && new_inode.metadata().uid != credentials.euid())
return EACCES;
}
if (new_inode.is_directory() && !old_inode.is_directory())
return EISDIR;
TRY(new_parent_inode.remove_child(new_basename));
}
TRY(new_parent_inode.add_child(old_inode, new_basename, old_inode.mode()));
TRY(old_parent_inode.remove_child(old_basename));
// If the inode that we moved is a directory and we changed parent
// directories, then we also have to make .. point to the new parent inode,
// because .. is its own inode.
if (old_inode.is_directory() && old_parent_inode.index() != new_parent_inode.index()) {
TRY(old_inode.replace_child(".."sv, new_parent_inode));
}
return {};
}
ErrorOr<void> VirtualFileSystem::chown(Credentials const& credentials, Custody& custody, UserID a_uid, GroupID a_gid)
{
auto& inode = custody.inode();
auto metadata = inode.metadata();
if (credentials.euid() != metadata.uid && !credentials.is_superuser())
return EPERM;
UserID new_uid = metadata.uid;
GroupID new_gid = metadata.gid;
if (a_uid != (uid_t)-1) {
if (credentials.euid() != a_uid && !credentials.is_superuser())
return EPERM;
new_uid = a_uid;
}
if (a_gid != (gid_t)-1) {
if (!credentials.in_group(a_gid) && !credentials.is_superuser())
return EPERM;
new_gid = a_gid;
}
if (custody.is_readonly())
return EROFS;
dbgln_if(VFS_DEBUG, "VirtualFileSystem::chown(): inode {} <- uid={} gid={}", inode.identifier(), new_uid, new_gid);
if (metadata.is_setuid() || metadata.is_setgid()) {
dbgln_if(VFS_DEBUG, "VirtualFileSystem::chown(): Stripping SUID/SGID bits from {}", inode.identifier());
TRY(inode.chmod(metadata.mode & ~(04000 | 02000)));
}
return inode.chown(new_uid, new_gid);
}
ErrorOr<void> VirtualFileSystem::chown(Credentials const& credentials, StringView path, UserID a_uid, GroupID a_gid, Custody& base, int options)
{
auto custody = TRY(resolve_path(credentials, path, base, nullptr, options));
return chown(credentials, custody, a_uid, a_gid);
}
static bool hard_link_allowed(Credentials const& credentials, Inode const& inode)
{
auto metadata = inode.metadata();
if (credentials.euid() == metadata.uid)
return true;
if (metadata.is_regular_file()
&& !metadata.is_setuid()
&& !(metadata.is_setgid() && metadata.mode & S_IXGRP)
&& metadata.may_write(credentials)) {
return true;
}
return false;
}
ErrorOr<void> VirtualFileSystem::link(Credentials const& credentials, StringView old_path, StringView new_path, Custody& base)
{
// NOTE: To prevent unveil bypass by creating an hardlink after unveiling a path as read-only,
// check that if write permission is allowed by the veil info on the old_path.
auto old_custody = TRY(resolve_path(credentials, old_path, base, nullptr, O_RDWR));
auto& old_inode = old_custody->inode();
RefPtr<Custody> parent_custody;
auto new_custody_or_error = resolve_path(credentials, new_path, base, &parent_custody);
if (!new_custody_or_error.is_error())
return EEXIST;
if (!parent_custody)
return ENOENT;
auto& parent_inode = parent_custody->inode();
if (parent_inode.fsid() != old_inode.fsid())
return EXDEV;
if (!parent_inode.metadata().may_write(credentials))
return EACCES;
if (old_inode.is_directory())
return EPERM;
if (parent_custody->is_readonly())
return EROFS;
if (!hard_link_allowed(credentials, old_inode))
return EPERM;
return parent_inode.add_child(old_inode, KLexicalPath::basename(new_path), old_inode.mode());
}
ErrorOr<void> VirtualFileSystem::unlink(Credentials const& credentials, StringView path, Custody& base)
{
RefPtr<Custody> parent_custody;
auto custody = TRY(resolve_path(credentials, path, base, &parent_custody, O_WRONLY | O_NOFOLLOW_NOERROR | O_UNLINK_INTERNAL));
auto& inode = custody->inode();
if (inode.is_directory())
return EISDIR;
// We have just checked that the inode is not a directory, and thus it's not
// the root. So it should have a parent. Note that this would be invalidated
// if we were to support bind-mounting regular files on top of the root.
VERIFY(parent_custody);
auto& parent_inode = parent_custody->inode();
if (!parent_inode.metadata().may_write(credentials))
return EACCES;
if (parent_inode.metadata().is_sticky()) {
if (!credentials.is_superuser() && parent_inode.metadata().uid != credentials.euid() && inode.metadata().uid != credentials.euid())
return EACCES;
}
if (parent_custody->is_readonly())
return EROFS;
return parent_inode.remove_child(KLexicalPath::basename(path));
}
ErrorOr<void> VirtualFileSystem::symlink(Credentials const& credentials, StringView target, StringView linkpath, Custody& base)
{
// NOTE: Check that the actual target (if it exists right now) is unveiled and prevent creating symlinks on veiled paths!
if (auto target_custody_or_error = resolve_path_without_veil(credentials, target, base, nullptr, O_RDWR, 0); !target_custody_or_error.is_error()) {
auto target_custody = target_custody_or_error.release_value();
TRY(validate_path_against_process_veil(*target_custody, O_RDWR));
}
RefPtr<Custody> parent_custody;
auto existing_custody_or_error = resolve_path(credentials, linkpath, base, &parent_custody, O_RDWR);
if (!existing_custody_or_error.is_error())
return EEXIST;
if (!parent_custody)
return ENOENT;
// NOTE: VERY IMPORTANT! We prevent creating symlinks in case the program didn't unveil the parent_custody
// path! For example, say the program wanted to create a symlink in /tmp/symlink to /tmp/test/pointee_symlink
// and unveiled the /tmp/test/ directory path beforehand, but not the /tmp directory path - the symlink syscall will
// fail here because we can't create the symlink in a parent directory path we didn't unveil beforehand.
TRY(validate_path_against_process_veil(*parent_custody, O_RDWR));
if (existing_custody_or_error.is_error() && existing_custody_or_error.error().code() != ENOENT)
return existing_custody_or_error.release_error();
auto& parent_inode = parent_custody->inode();
if (!parent_inode.metadata().may_write(credentials))
return EACCES;
if (parent_custody->is_readonly())
return EROFS;
auto basename = KLexicalPath::basename(linkpath);
dbgln_if(VFS_DEBUG, "VirtualFileSystem::symlink: '{}' (-> '{}') in {}", basename, target, parent_inode.identifier());
auto inode = TRY(parent_inode.create_child(basename, S_IFLNK | 0644, 0, credentials.euid(), credentials.egid()));
auto target_buffer = UserOrKernelBuffer::for_kernel_buffer(const_cast<u8*>((u8 const*)target.characters_without_null_termination()));
TRY(inode->write_bytes(0, target.length(), target_buffer, nullptr));
return {};
}
// https://pubs.opengroup.org/onlinepubs/9699919799/functions/rmdir.html
ErrorOr<void> VirtualFileSystem::rmdir(Credentials const& credentials, StringView path, Custody& base)
{
RefPtr<Custody> parent_custody;
auto custody = TRY(resolve_path(credentials, path, base, &parent_custody, O_CREAT));
auto& inode = custody->inode();
auto last_component = KLexicalPath::basename(path);
// [EINVAL] The path argument contains a last component that is dot.
if (last_component == "."sv)
return EINVAL;
// [ENOTDIR] A component of path names an existing file that is neither a directory
// nor a symbolic link to a directory.
if (!inode.is_directory())
return ENOTDIR;
// [EBUSY] The directory to be removed is currently in use by the system or some process
// and the implementation considers this to be an error.
// NOTE: If there is no parent, that means we're trying to rmdir the root directory!
if (!parent_custody)
return EBUSY;
auto& parent_inode = parent_custody->inode();
auto parent_metadata = parent_inode.metadata();
// [EACCES] Search permission is denied on a component of the path prefix,
// or write permission is denied on the parent directory of the directory to be removed.
if (!parent_metadata.may_write(credentials))
return EACCES;
if (parent_metadata.is_sticky()) {
// [EACCES] The S_ISVTX flag is set on the directory containing the file referred to by the path argument
// and the process does not satisfy the criteria specified in XBD Directory Protection.
if (!credentials.is_superuser()
&& inode.metadata().uid != credentials.euid()
&& parent_metadata.uid != credentials.euid()) {
return EACCES;
}
}
size_t child_count = 0;
TRY(inode.traverse_as_directory([&child_count](auto&) -> ErrorOr<void> {
++child_count;
return {};
}));
// [ENOTEMPTY] The path argument names a directory that is not an empty directory,
// or there are hard links to the directory other than dot or a single entry in dot-dot.
if (child_count != 2)
return ENOTEMPTY;
// [EROFS] The directory entry to be removed resides on a read-only file system.
if (custody->is_readonly())
return EROFS;
TRY(inode.remove_child("."sv));
TRY(inode.remove_child(".."sv));
return parent_inode.remove_child(KLexicalPath::basename(path));
}
ErrorOr<void> VirtualFileSystem::for_each_mount(Function<ErrorOr<void>(Mount const&)> callback) const
{
return m_mounts.with([&](auto& mounts) -> ErrorOr<void> {
for (auto& mount : mounts)
TRY(callback(mount));
return {};
});
}
void VirtualFileSystem::sync()
{
FileSystem::sync();
}
NonnullRefPtr<Custody> VirtualFileSystem::root_custody()
{
return m_root_custody.with([](auto& root_custody) -> NonnullRefPtr<Custody> { return *root_custody; });
}
UnveilNode const& VirtualFileSystem::find_matching_unveiled_path(Process const& process, StringView path)
{
VERIFY(process.veil_state() != VeilState::None);
return process.unveil_data().with([&](auto const& unveil_data) -> UnveilNode const& {
auto path_parts = KLexicalPath::parts(path);
return unveil_data.paths.traverse_until_last_accessible_node(path_parts.begin(), path_parts.end());
});
}
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(Custody const& custody, int options)
{
return validate_path_against_process_veil(Process::current(), custody, options);
}
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(Process const& process, Custody const& custody, int options)
{
if (process.veil_state() == VeilState::None)
return {};
auto absolute_path = TRY(custody.try_serialize_absolute_path());
return validate_path_against_process_veil(process, absolute_path->view(), options);
}
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(Process const& process, StringView path, int options)
{
if (process.veil_state() == VeilState::None)
return {};
VERIFY(path.starts_with('/'));
VERIFY(!path.contains("/../"sv) && !path.ends_with("/.."sv));
VERIFY(!path.contains("/./"sv) && !path.ends_with("/."sv));
#ifdef SKIP_PATH_VALIDATION_FOR_COVERAGE_INSTRUMENTATION
// Skip veil validation against profile data when coverage is enabled for userspace
// so that all processes can write out coverage data even with veils in place
if (KLexicalPath::basename(path).ends_with(".profraw"sv))
return {};
#endif
auto log_veiled_path = [&](Optional<StringView> const& with_permissions = {}) {
if (with_permissions.has_value())
dbgln("\033[31;1mRejecting path '{}' because it hasn't been unveiled with {} permissions\033[0m", path, *with_permissions);
else
dbgln("\033[31;1mRejecting path '{}' because it hasn't been unveiled\033[0m", path);
dump_backtrace();
};
auto& unveiled_path = find_matching_unveiled_path(process, path);
if (unveiled_path.permissions() == UnveilAccess::None) {
log_veiled_path();
return ENOENT;
}
if (options & O_CREAT) {
if (!(unveiled_path.permissions() & UnveilAccess::CreateOrRemove)) {
log_veiled_path("'c'"sv);
return EACCES;
}
}
if (options & O_UNLINK_INTERNAL) {
if (!(unveiled_path.permissions() & UnveilAccess::CreateOrRemove)) {
log_veiled_path("'c'"sv);
return EACCES;
}
return {};
}
if (options & O_RDONLY) {
if (options & O_DIRECTORY) {
if (!(unveiled_path.permissions() & (UnveilAccess::Read | UnveilAccess::Browse))) {
log_veiled_path("'r' or 'b'"sv);
return EACCES;
}
} else {
if (!(unveiled_path.permissions() & UnveilAccess::Read)) {
log_veiled_path("'r'"sv);
return EACCES;
}
}
}
if (options & O_WRONLY) {
if (!(unveiled_path.permissions() & UnveilAccess::Write)) {
log_veiled_path("'w'"sv);
return EACCES;
}
}
if (options & O_EXEC) {
if (!(unveiled_path.permissions() & UnveilAccess::Execute)) {
log_veiled_path("'x'"sv);
return EACCES;
}
}
return {};
}
ErrorOr<void> VirtualFileSystem::validate_path_against_process_veil(StringView path, int options)
{
return validate_path_against_process_veil(Process::current(), path, options);
}
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path(Credentials const& credentials, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
{
return resolve_path(Process::current(), credentials, path, base, out_parent, options, symlink_recursion_level);
}
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path(Process const& process, Credentials const& credentials, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
{
// FIXME: The errors returned by resolve_path_without_veil can leak information about paths that are not unveiled,
// e.g. when the error is EACCESS or similar.
auto custody = TRY(resolve_path_without_veil(credentials, path, base, out_parent, options, symlink_recursion_level));
if (auto result = validate_path_against_process_veil(process, *custody, options); result.is_error()) {
if (out_parent)
out_parent->clear();
return result.release_error();
}
return custody;
}
static bool safe_to_follow_symlink(Credentials const& credentials, Inode const& inode, InodeMetadata const& parent_metadata)
{
auto metadata = inode.metadata();
if (credentials.euid() == metadata.uid)
return true;
if (!(parent_metadata.is_sticky() && parent_metadata.mode & S_IWOTH))
return true;
if (metadata.uid == parent_metadata.uid)
return true;
return false;
}
ErrorOr<NonnullRefPtr<Custody>> VirtualFileSystem::resolve_path_without_veil(Credentials const& credentials, StringView path, NonnullRefPtr<Custody> base, RefPtr<Custody>* out_parent, int options, int symlink_recursion_level)
{
if (symlink_recursion_level >= symlink_recursion_limit)
return ELOOP;
if (path.is_empty())
return EINVAL;
GenericLexer path_lexer(path);
NonnullRefPtr<Custody> custody = path[0] == '/' ? root_custody() : base;
bool extra_iteration = path[path.length() - 1] == '/';
while (!path_lexer.is_eof() || extra_iteration) {
if (path_lexer.is_eof())
extra_iteration = false;
auto part = path_lexer.consume_until('/');
path_lexer.ignore();
Custody& parent = custody;
auto parent_metadata = parent.inode().metadata();
if (!parent_metadata.is_directory())
return ENOTDIR;
// Ensure the current user is allowed to resolve paths inside this directory.
if (!parent_metadata.may_execute(credentials))
return EACCES;
bool have_more_parts = !path_lexer.is_eof() || extra_iteration;
if (part == "..") {
// If we encounter a "..", take a step back, but don't go beyond the root.
if (custody->parent())
custody = *custody->parent();
continue;
} else if (part == "." || part.is_empty()) {
continue;
}
// Okay, let's look up this part.
auto child_or_error = parent.inode().lookup(part);
if (child_or_error.is_error()) {
if (out_parent) {
// ENOENT with a non-null parent custody signals to caller that
// we found the immediate parent of the file, but the file itself
// does not exist yet.
*out_parent = have_more_parts ? nullptr : &parent;
}
return child_or_error.release_error();
}
auto child_inode = child_or_error.release_value();
int mount_flags_for_child = parent.mount_flags();
auto current_custody = TRY(Custody::try_create(&parent, part, *child_inode, mount_flags_for_child));
// See if there's something mounted on the child; in that case
// we would need to return the guest inode, not the host inode.
if (auto mount = find_mount_for_host_custody(current_custody)) {
child_inode = mount->guest();
mount_flags_for_child = mount->flags();
custody = TRY(Custody::try_create(&parent, part, *child_inode, mount_flags_for_child));
} else {
custody = current_custody;
}
if (child_inode->metadata().is_symlink()) {
if (!have_more_parts) {
if (options & O_NOFOLLOW)
return ELOOP;
if (options & O_NOFOLLOW_NOERROR)
break;
}
if (!safe_to_follow_symlink(credentials, *child_inode, parent_metadata))
return EACCES;
TRY(validate_path_against_process_veil(*custody, options));
auto symlink_target = TRY(child_inode->resolve_as_link(credentials, parent, out_parent, options, symlink_recursion_level + 1));
if (!have_more_parts)
return symlink_target;
// Now, resolve the remaining path relative to the symlink target.
// We prepend a "." to it to ensure that it's not empty and that
// any initial slashes it might have get interpreted properly.
StringBuilder remaining_path;
TRY(remaining_path.try_append('.'));
TRY(remaining_path.try_append(path.substring_view_starting_after_substring(part)));
return resolve_path_without_veil(credentials, remaining_path.string_view(), symlink_target, out_parent, options, symlink_recursion_level + 1);
}
}
if (out_parent)
*out_parent = custody->parent();
return custody;
}
}
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