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c8d9f1b9c9
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.
145 lines
5.2 KiB
C++
145 lines
5.2 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <Kernel/FileSystem/Custody.h>
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#include <Kernel/FileSystem/DevPtsFS.h>
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#include <Kernel/FileSystem/Ext2FileSystem.h>
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#include <Kernel/FileSystem/Plan9FileSystem.h>
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#include <Kernel/FileSystem/ProcFS.h>
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#include <Kernel/FileSystem/TmpFS.h>
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#include <Kernel/FileSystem/VirtualFileSystem.h>
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#include <Kernel/Process.h>
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namespace Kernel {
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int Process::sys$mount(Userspace<const Syscall::SC_mount_params*> user_params)
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{
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if (!is_superuser())
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return -EPERM;
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REQUIRE_NO_PROMISES;
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Syscall::SC_mount_params params;
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if (!copy_from_user(¶ms, user_params))
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return -EFAULT;
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auto source_fd = params.source_fd;
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auto target = copy_string_from_user(params.target);
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if (target.is_null())
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return -EFAULT;
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auto fs_type = copy_string_from_user(params.fs_type);
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if (fs_type.is_null())
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return -EFAULT;
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auto description = file_description(source_fd);
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if (!description.is_null())
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dbg() << "mount " << fs_type << ": source fd " << source_fd << " @ " << target;
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else
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dbg() << "mount " << fs_type << " @ " << target;
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auto custody_or_error = VFS::the().resolve_path(target, current_directory());
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if (custody_or_error.is_error())
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return custody_or_error.error();
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auto& target_custody = custody_or_error.value();
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if (params.flags & MS_REMOUNT) {
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// We're not creating a new mount, we're updating an existing one!
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return VFS::the().remount(target_custody, params.flags & ~MS_REMOUNT);
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}
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if (params.flags & MS_BIND) {
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// We're doing a bind mount.
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if (description.is_null())
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return -EBADF;
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if (!description->custody()) {
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// We only support bind-mounting inodes, not arbitrary files.
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return -ENODEV;
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}
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return VFS::the().bind_mount(*description->custody(), target_custody, params.flags);
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}
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RefPtr<FS> fs;
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if (fs_type == "ext2" || fs_type == "Ext2FS") {
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if (description.is_null())
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return -EBADF;
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if (!description->file().is_seekable()) {
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dbg() << "mount: this is not a seekable file";
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return -ENODEV;
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}
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dbg() << "mount: attempting to mount " << description->absolute_path() << " on " << target;
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fs = Ext2FS::create(*description);
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} else if (fs_type == "9p" || fs_type == "Plan9FS") {
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if (description.is_null())
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return -EBADF;
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fs = Plan9FS::create(*description);
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} else if (fs_type == "proc" || fs_type == "ProcFS") {
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fs = ProcFS::create();
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} else if (fs_type == "devpts" || fs_type == "DevPtsFS") {
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fs = DevPtsFS::create();
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} else if (fs_type == "tmp" || fs_type == "TmpFS") {
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fs = TmpFS::create();
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} else {
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return -ENODEV;
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}
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if (!fs->initialize()) {
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dbg() << "mount: failed to initialize " << fs_type << " filesystem, fd - " << source_fd;
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return -ENODEV;
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}
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auto result = VFS::the().mount(fs.release_nonnull(), target_custody, params.flags);
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if (!description.is_null())
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dbg() << "mount: successfully mounted " << description->absolute_path() << " on " << target;
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else
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dbg() << "mount: successfully mounted " << target;
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return result;
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}
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int Process::sys$umount(Userspace<const char*> user_mountpoint, size_t mountpoint_length)
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{
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if (!is_superuser())
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return -EPERM;
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REQUIRE_NO_PROMISES;
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auto mountpoint = get_syscall_path_argument(user_mountpoint, mountpoint_length);
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if (mountpoint.is_error())
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return mountpoint.error();
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auto custody_or_error = VFS::the().resolve_path(mountpoint.value(), current_directory());
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if (custody_or_error.is_error())
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return custody_or_error.error();
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auto& guest_inode = custody_or_error.value()->inode();
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return VFS::the().unmount(guest_inode);
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}
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}
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