389 lines
11 KiB
Go
389 lines
11 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package vfs2
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import (
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/bits"
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"gvisor.dev/gvisor/pkg/fspath"
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"gvisor.dev/gvisor/pkg/gohacks"
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"gvisor.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/syserror"
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"gvisor.dev/gvisor/pkg/usermem"
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)
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// Stat implements Linux syscall stat(2).
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func Stat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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pathAddr := args[0].Pointer()
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statAddr := args[1].Pointer()
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return 0, nil, fstatat(t, linux.AT_FDCWD, pathAddr, statAddr, 0 /* flags */)
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}
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// Lstat implements Linux syscall lstat(2).
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func Lstat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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pathAddr := args[0].Pointer()
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statAddr := args[1].Pointer()
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return 0, nil, fstatat(t, linux.AT_FDCWD, pathAddr, statAddr, linux.AT_SYMLINK_NOFOLLOW)
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}
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// Newfstatat implements Linux syscall newfstatat, which backs fstatat(2).
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func Newfstatat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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dirfd := args[0].Int()
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pathAddr := args[1].Pointer()
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statAddr := args[2].Pointer()
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flags := args[3].Int()
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return 0, nil, fstatat(t, dirfd, pathAddr, statAddr, flags)
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}
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func fstatat(t *kernel.Task, dirfd int32, pathAddr, statAddr usermem.Addr, flags int32) error {
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if flags&^(linux.AT_EMPTY_PATH|linux.AT_SYMLINK_NOFOLLOW) != 0 {
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return syserror.EINVAL
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}
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opts := vfs.StatOptions{
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Mask: linux.STATX_BASIC_STATS,
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}
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path, err := copyInPath(t, pathAddr)
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if err != nil {
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return err
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}
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root := t.FSContext().RootDirectoryVFS2()
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defer root.DecRef()
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start := root
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if !path.Absolute {
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if !path.HasComponents() && flags&linux.AT_EMPTY_PATH == 0 {
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return syserror.ENOENT
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}
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if dirfd == linux.AT_FDCWD {
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start = t.FSContext().WorkingDirectoryVFS2()
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defer start.DecRef()
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} else {
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dirfile := t.GetFileVFS2(dirfd)
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if dirfile == nil {
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return syserror.EBADF
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}
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if !path.HasComponents() {
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// Use FileDescription.Stat() instead of
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// VirtualFilesystem.StatAt() for fstatat(fd, ""), since the
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// former may be able to use opened file state to expedite the
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// Stat.
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statx, err := dirfile.Stat(t, opts)
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dirfile.DecRef()
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if err != nil {
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return err
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}
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var stat linux.Stat
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convertStatxToUserStat(t, &statx, &stat)
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_, err = stat.CopyOut(t, statAddr)
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return err
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}
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start = dirfile.VirtualDentry()
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start.IncRef()
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defer start.DecRef()
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dirfile.DecRef()
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}
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}
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statx, err := t.Kernel().VFS().StatAt(t, t.Credentials(), &vfs.PathOperation{
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Root: root,
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Start: start,
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Path: path,
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FollowFinalSymlink: flags&linux.AT_SYMLINK_NOFOLLOW == 0,
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}, &opts)
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if err != nil {
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return err
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}
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var stat linux.Stat
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convertStatxToUserStat(t, &statx, &stat)
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_, err = stat.CopyOut(t, statAddr)
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return err
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}
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func timespecFromStatxTimestamp(sxts linux.StatxTimestamp) linux.Timespec {
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return linux.Timespec{
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Sec: sxts.Sec,
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Nsec: int64(sxts.Nsec),
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}
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}
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// Fstat implements Linux syscall fstat(2).
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func Fstat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := args[0].Int()
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statAddr := args[1].Pointer()
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file := t.GetFileVFS2(fd)
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if file == nil {
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return 0, nil, syserror.EBADF
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}
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defer file.DecRef()
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statx, err := file.Stat(t, vfs.StatOptions{
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Mask: linux.STATX_BASIC_STATS,
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})
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if err != nil {
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return 0, nil, err
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}
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var stat linux.Stat
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convertStatxToUserStat(t, &statx, &stat)
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_, err = stat.CopyOut(t, statAddr)
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return 0, nil, err
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}
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// Statx implements Linux syscall statx(2).
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func Statx(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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dirfd := args[0].Int()
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pathAddr := args[1].Pointer()
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flags := args[2].Int()
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mask := args[3].Uint()
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statxAddr := args[4].Pointer()
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if flags&^(linux.AT_EMPTY_PATH|linux.AT_SYMLINK_NOFOLLOW|linux.AT_STATX_SYNC_TYPE) != 0 {
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return 0, nil, syserror.EINVAL
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}
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// Make sure that only one sync type option is set.
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syncType := uint32(flags & linux.AT_STATX_SYNC_TYPE)
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if syncType != 0 && !bits.IsPowerOfTwo32(syncType) {
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return 0, nil, syserror.EINVAL
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}
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if mask&linux.STATX__RESERVED != 0 {
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return 0, nil, syserror.EINVAL
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}
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opts := vfs.StatOptions{
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Mask: mask,
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Sync: uint32(flags & linux.AT_STATX_SYNC_TYPE),
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}
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path, err := copyInPath(t, pathAddr)
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if err != nil {
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return 0, nil, err
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}
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root := t.FSContext().RootDirectoryVFS2()
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defer root.DecRef()
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start := root
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if !path.Absolute {
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if !path.HasComponents() && flags&linux.AT_EMPTY_PATH == 0 {
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return 0, nil, syserror.ENOENT
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}
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if dirfd == linux.AT_FDCWD {
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start = t.FSContext().WorkingDirectoryVFS2()
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defer start.DecRef()
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} else {
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dirfile := t.GetFileVFS2(dirfd)
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if dirfile == nil {
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return 0, nil, syserror.EBADF
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}
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if !path.HasComponents() {
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// Use FileDescription.Stat() instead of
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// VirtualFilesystem.StatAt() for statx(fd, ""), since the
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// former may be able to use opened file state to expedite the
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// Stat.
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statx, err := dirfile.Stat(t, opts)
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dirfile.DecRef()
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if err != nil {
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return 0, nil, err
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}
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userifyStatx(t, &statx)
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_, err = statx.CopyOut(t, statxAddr)
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return 0, nil, err
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}
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start = dirfile.VirtualDentry()
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start.IncRef()
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defer start.DecRef()
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dirfile.DecRef()
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}
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}
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statx, err := t.Kernel().VFS().StatAt(t, t.Credentials(), &vfs.PathOperation{
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Root: root,
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Start: start,
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Path: path,
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FollowFinalSymlink: flags&linux.AT_SYMLINK_NOFOLLOW == 0,
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}, &opts)
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if err != nil {
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return 0, nil, err
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}
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userifyStatx(t, &statx)
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_, err = statx.CopyOut(t, statxAddr)
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return 0, nil, err
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}
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func userifyStatx(t *kernel.Task, statx *linux.Statx) {
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userns := t.UserNamespace()
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statx.UID = uint32(auth.KUID(statx.UID).In(userns).OrOverflow())
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statx.GID = uint32(auth.KGID(statx.GID).In(userns).OrOverflow())
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}
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// Readlink implements Linux syscall readlink(2).
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func Readlink(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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pathAddr := args[0].Pointer()
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bufAddr := args[1].Pointer()
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size := args[2].SizeT()
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return readlinkat(t, linux.AT_FDCWD, pathAddr, bufAddr, size)
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}
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// Access implements Linux syscall access(2).
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func Access(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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addr := args[0].Pointer()
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mode := args[1].ModeT()
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return 0, nil, accessAt(t, linux.AT_FDCWD, addr, mode)
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}
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// Faccessat implements Linux syscall faccessat(2).
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//
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// Note that the faccessat() system call does not take a flags argument:
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// "The raw faccessat() system call takes only the first three arguments. The
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// AT_EACCESS and AT_SYMLINK_NOFOLLOW flags are actually implemented within
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// the glibc wrapper function for faccessat(). If either of these flags is
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// specified, then the wrapper function employs fstatat(2) to determine access
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// permissions." - faccessat(2)
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func Faccessat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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dirfd := args[0].Int()
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addr := args[1].Pointer()
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mode := args[2].ModeT()
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return 0, nil, accessAt(t, dirfd, addr, mode)
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}
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func accessAt(t *kernel.Task, dirfd int32, pathAddr usermem.Addr, mode uint) error {
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const rOK = 4
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const wOK = 2
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const xOK = 1
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// Sanity check the mode.
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if mode&^(rOK|wOK|xOK) != 0 {
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return syserror.EINVAL
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}
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path, err := copyInPath(t, pathAddr)
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if err != nil {
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return err
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}
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tpop, err := getTaskPathOperation(t, dirfd, path, disallowEmptyPath, followFinalSymlink)
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if err != nil {
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return err
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}
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defer tpop.Release()
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// access(2) and faccessat(2) check permissions using real
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// UID/GID, not effective UID/GID.
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//
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// "access() needs to use the real uid/gid, not the effective
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// uid/gid. We do this by temporarily clearing all FS-related
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// capabilities and switching the fsuid/fsgid around to the
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// real ones." -fs/open.c:faccessat
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creds := t.Credentials().Fork()
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creds.EffectiveKUID = creds.RealKUID
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creds.EffectiveKGID = creds.RealKGID
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if creds.EffectiveKUID.In(creds.UserNamespace) == auth.RootUID {
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creds.EffectiveCaps = creds.PermittedCaps
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} else {
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creds.EffectiveCaps = 0
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}
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return t.Kernel().VFS().AccessAt(t, creds, vfs.AccessTypes(mode), &tpop.pop)
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}
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// Readlinkat implements Linux syscall mknodat(2).
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func Readlinkat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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dirfd := args[0].Int()
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pathAddr := args[1].Pointer()
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bufAddr := args[2].Pointer()
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size := args[3].SizeT()
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return readlinkat(t, dirfd, pathAddr, bufAddr, size)
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}
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func readlinkat(t *kernel.Task, dirfd int32, pathAddr, bufAddr usermem.Addr, size uint) (uintptr, *kernel.SyscallControl, error) {
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if int(size) <= 0 {
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return 0, nil, syserror.EINVAL
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}
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path, err := copyInPath(t, pathAddr)
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if err != nil {
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return 0, nil, err
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}
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// "Since Linux 2.6.39, pathname can be an empty string, in which case the
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// call operates on the symbolic link referred to by dirfd ..." -
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// readlinkat(2)
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tpop, err := getTaskPathOperation(t, dirfd, path, allowEmptyPath, nofollowFinalSymlink)
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if err != nil {
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return 0, nil, err
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}
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defer tpop.Release()
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target, err := t.Kernel().VFS().ReadlinkAt(t, t.Credentials(), &tpop.pop)
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if err != nil {
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return 0, nil, err
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}
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if len(target) > int(size) {
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target = target[:size]
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}
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n, err := t.CopyOutBytes(bufAddr, gohacks.ImmutableBytesFromString(target))
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if n == 0 {
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return 0, nil, err
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}
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return uintptr(n), nil, nil
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}
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// Statfs implements Linux syscall statfs(2).
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func Statfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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pathAddr := args[0].Pointer()
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bufAddr := args[1].Pointer()
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path, err := copyInPath(t, pathAddr)
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if err != nil {
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return 0, nil, err
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}
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tpop, err := getTaskPathOperation(t, linux.AT_FDCWD, path, disallowEmptyPath, followFinalSymlink)
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if err != nil {
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return 0, nil, err
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}
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defer tpop.Release()
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statfs, err := t.Kernel().VFS().StatFSAt(t, t.Credentials(), &tpop.pop)
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if err != nil {
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return 0, nil, err
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}
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_, err = statfs.CopyOut(t, bufAddr)
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return 0, nil, err
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}
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// Fstatfs implements Linux syscall fstatfs(2).
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func Fstatfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := args[0].Int()
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bufAddr := args[1].Pointer()
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tpop, err := getTaskPathOperation(t, fd, fspath.Path{}, allowEmptyPath, nofollowFinalSymlink)
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if err != nil {
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return 0, nil, err
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}
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defer tpop.Release()
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statfs, err := t.Kernel().VFS().StatFSAt(t, t.Credentials(), &tpop.pop)
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if err != nil {
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return 0, nil, err
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}
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_, err = statfs.CopyOut(t, bufAddr)
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return 0, nil, err
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}
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