170 lines
4.5 KiB
Go
170 lines
4.5 KiB
Go
// Copyright 2019 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 linux
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import (
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"strings"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/sentry/arch"
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"gvisor.dev/gvisor/pkg/sentry/fs"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/sentry/usermem"
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"gvisor.dev/gvisor/pkg/syserror"
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)
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// Getxattr implements linux syscall getxattr(2).
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func Getxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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pathAddr := args[0].Pointer()
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nameAddr := args[1].Pointer()
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valueAddr := args[2].Pointer()
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size := args[3].SizeT()
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path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */)
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if err != nil {
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return 0, nil, err
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}
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valueLen := 0
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err = fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
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value, err := getxattr(t, d, dirPath, nameAddr)
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if err != nil {
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return err
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}
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valueLen = len(value)
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if size == 0 {
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return nil
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}
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if size > linux.XATTR_SIZE_MAX {
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size = linux.XATTR_SIZE_MAX
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}
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if valueLen > int(size) {
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return syserror.ERANGE
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}
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_, err = t.CopyOutBytes(valueAddr, []byte(value))
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return err
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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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return uintptr(valueLen), nil, nil
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}
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// getxattr implements getxattr from the given *fs.Dirent.
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func getxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr usermem.Addr) (string, error) {
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if dirPath && !fs.IsDir(d.Inode.StableAttr) {
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return "", syserror.ENOTDIR
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}
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if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Read: true}); err != nil {
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return "", err
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}
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name, err := copyInXattrName(t, nameAddr)
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if err != nil {
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return "", err
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}
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if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
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return "", syserror.EOPNOTSUPP
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}
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return d.Inode.Getxattr(name)
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}
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// Setxattr implements linux syscall setxattr(2).
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func Setxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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pathAddr := args[0].Pointer()
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nameAddr := args[1].Pointer()
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valueAddr := args[2].Pointer()
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size := args[3].SizeT()
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flags := args[4].Uint()
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path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */)
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if err != nil {
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return 0, nil, err
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}
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if flags&^(linux.XATTR_CREATE|linux.XATTR_REPLACE) != 0 {
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return 0, nil, syserror.EINVAL
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}
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return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
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return setxattr(t, d, dirPath, nameAddr, valueAddr, size, flags)
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})
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}
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// setxattr implements setxattr from the given *fs.Dirent.
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func setxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr usermem.Addr, size uint, flags uint32) error {
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if dirPath && !fs.IsDir(d.Inode.StableAttr) {
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return syserror.ENOTDIR
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}
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if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Write: true}); err != nil {
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return err
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}
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name, err := copyInXattrName(t, nameAddr)
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if err != nil {
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return err
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}
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if size > linux.XATTR_SIZE_MAX {
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return syserror.E2BIG
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}
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buf := make([]byte, size)
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if _, err = t.CopyInBytes(valueAddr, buf); err != nil {
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return err
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}
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value := string(buf)
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if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
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return syserror.EOPNOTSUPP
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}
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return d.Inode.Setxattr(name, value)
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}
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func copyInXattrName(t *kernel.Task, nameAddr usermem.Addr) (string, error) {
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name, err := t.CopyInString(nameAddr, linux.XATTR_NAME_MAX+1)
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if err != nil {
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if err == syserror.ENAMETOOLONG {
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return "", syserror.ERANGE
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}
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return "", err
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}
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if len(name) == 0 {
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return "", syserror.ERANGE
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}
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return name, nil
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}
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func checkXattrPermissions(t *kernel.Task, i *fs.Inode, perms fs.PermMask) error {
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// Restrict xattrs to regular files and directories.
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//
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// In Linux, this restriction technically only applies to xattrs in the
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// "user.*" namespace, but we don't allow any other xattr prefixes anyway.
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if !fs.IsRegular(i.StableAttr) && !fs.IsDir(i.StableAttr) {
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if perms.Write {
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return syserror.EPERM
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}
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return syserror.ENODATA
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}
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return i.CheckPermission(t, perms)
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}
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