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https://github.com/SerenityOS/serenity
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d8b514873f
Using the kernel stack is preferable, especially when the examined strings should be limited to a reasonable length. This is a small improvement, because if we don't actually move these strings then we don't need to own heap allocations for them during the syscall handler function scope. In addition to that, some kernel strings are known to be limited, like the hostname string, for these strings we also can use FixedStringBuffer to store and copy to and from these buffers, without using any heap allocations at all.
128 lines
4.9 KiB
C++
128 lines
4.9 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/FixedStringBuffer.h>
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#include <Kernel/FileSystem/Custody.h>
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#include <Kernel/FileSystem/MountFile.h>
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#include <Kernel/FileSystem/VirtualFileSystem.h>
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#include <Kernel/Tasks/Process.h>
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namespace Kernel {
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ErrorOr<FlatPtr> Process::sys$fsopen(Userspace<Syscall::SC_fsopen_params const*> user_params)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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TRY(require_promise(Pledge::mount));
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auto credentials = this->credentials();
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if (!credentials->is_superuser())
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return Error::from_errno(EPERM);
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auto params = TRY(copy_typed_from_user(user_params));
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// NOTE: 16 characters should be enough for any fstype today and in the future.
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auto fs_type_string = TRY(get_syscall_name_string_fixed_buffer<16>(params.fs_type));
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// NOTE: If some userspace program uses MS_REMOUNT, return EINVAL to indicate that we never want this
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// flag to appear in the mount table...
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if (params.flags & MS_REMOUNT || params.flags & MS_BIND)
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return Error::from_errno(EINVAL);
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auto const* fs_type_initializer = TRY(VirtualFileSystem::find_filesystem_type_initializer(fs_type_string.representable_view()));
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VERIFY(fs_type_initializer);
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auto mount_file = TRY(MountFile::create(*fs_type_initializer, params.flags));
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auto description = TRY(OpenFileDescription::try_create(move(mount_file)));
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return m_fds.with_exclusive([&](auto& fds) -> ErrorOr<FlatPtr> {
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auto new_fd = TRY(fds.allocate());
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fds[new_fd.fd].set(move(description), FD_CLOEXEC);
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return new_fd.fd;
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});
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}
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ErrorOr<FlatPtr> Process::sys$fsmount(Userspace<Syscall::SC_fsmount_params const*> user_params)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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TRY(require_promise(Pledge::mount));
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auto credentials = this->credentials();
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if (!credentials->is_superuser())
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return Error::from_errno(EPERM);
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auto params = TRY(copy_typed_from_user(user_params));
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auto mount_description = TRY(open_file_description(params.mount_fd));
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if (!mount_description->is_mount_file())
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return Error::from_errno(EINVAL);
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RefPtr<OpenFileDescription> source_description = TRY(open_file_description_ignoring_negative(params.source_fd));
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auto target = TRY(try_copy_kstring_from_user(params.target));
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auto target_custody = TRY(VirtualFileSystem::the().resolve_path(credentials, target->view(), current_directory()));
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auto flags = mount_description->mount_file()->mount_flags();
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TRY(VirtualFileSystem::the().mount(*mount_description->mount_file(), source_description.ptr(), target_custody, flags));
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return 0;
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}
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ErrorOr<FlatPtr> Process::sys$remount(Userspace<Syscall::SC_remount_params const*> user_params)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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TRY(require_promise(Pledge::mount));
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auto credentials = this->credentials();
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if (!credentials->is_superuser())
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return EPERM;
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auto params = TRY(copy_typed_from_user(user_params));
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if (params.flags & MS_REMOUNT)
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return EINVAL;
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if (params.flags & MS_BIND)
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return EINVAL;
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auto target = TRY(try_copy_kstring_from_user(params.target));
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auto target_custody = TRY(VirtualFileSystem::the().resolve_path(credentials, target->view(), current_directory()));
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TRY(VirtualFileSystem::the().remount(target_custody, params.flags));
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return 0;
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}
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ErrorOr<FlatPtr> Process::sys$bindmount(Userspace<Syscall::SC_bindmount_params const*> user_params)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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TRY(require_promise(Pledge::mount));
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auto credentials = this->credentials();
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if (!credentials->is_superuser())
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return EPERM;
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auto params = TRY(copy_typed_from_user(user_params));
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if (params.flags & MS_REMOUNT)
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return EINVAL;
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if (params.flags & MS_BIND)
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return EINVAL;
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auto source_fd = params.source_fd;
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auto target = TRY(try_copy_kstring_from_user(params.target));
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auto target_custody = TRY(VirtualFileSystem::the().resolve_path(credentials, target->view(), current_directory()));
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auto description = TRY(open_file_description(source_fd));
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if (!description->custody()) {
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// NOTE: We only support bind-mounting inodes, not arbitrary files.
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return ENODEV;
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}
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TRY(VirtualFileSystem::the().bind_mount(*description->custody(), target_custody, params.flags));
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return 0;
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}
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ErrorOr<FlatPtr> Process::sys$umount(Userspace<char const*> user_mountpoint, size_t mountpoint_length)
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{
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VERIFY_NO_PROCESS_BIG_LOCK(this);
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auto credentials = this->credentials();
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if (!credentials->is_superuser())
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return EPERM;
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TRY(require_promise(Pledge::mount));
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auto mountpoint = TRY(get_syscall_path_argument(user_mountpoint, mountpoint_length));
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auto custody = TRY(VirtualFileSystem::the().resolve_path(credentials, mountpoint->view(), current_directory()));
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TRY(VirtualFileSystem::the().unmount(*custody));
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return 0;
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}
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}
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