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23a7ccf607
This is a preparation before we can create a usable mechanism to use filesystem-specific mount flags. To keep some compatibility with userland code, LibC and LibCore mount functions are kept being usable, but now instead of doing an "atomic" syscall, they do multiple syscalls to perform the complete procedure of mounting a filesystem. The FileBackedFileSystem IntrusiveList in the VFS code is now changed to be protected by a Mutex, because when we mount a new filesystem, we need to check if a filesystem is already created for a given source_fd so we do a scan for that OpenFileDescription in that list. If we fail to find an already-created filesystem we create a new one and register it in the list if we successfully mounted it. We use a Mutex because we might need to initiate disk access during the filesystem creation, which will take other mutexes in other parts of the kernel, therefore making it not possible to take a spinlock while doing this.
125 lines
4.8 KiB
C++
125 lines
4.8 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 <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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auto fs_type_string = TRY(try_copy_kstring_from_user(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->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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