243 lines
6.9 KiB
Go
243 lines
6.9 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/syserror"
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"gvisor.dev/gvisor/pkg/usermem"
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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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return getXattrFromPath(t, args, true)
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}
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// LGetXattr implements linux syscall lgetxattr(2).
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func LGetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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return getXattrFromPath(t, args, false)
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}
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// FGetXattr implements linux syscall fgetxattr(2).
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func FGetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := args[0].Int()
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nameAddr := args[1].Pointer()
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valueAddr := args[2].Pointer()
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size := uint64(args[3].SizeT())
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// TODO(b/113957122): Return EBADF if the fd was opened with O_PATH.
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f := t.GetFile(fd)
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if f == nil {
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return 0, nil, syserror.EBADF
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}
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defer f.DecRef()
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n, value, err := getXattr(t, f.Dirent, nameAddr, size)
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if err != nil {
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return 0, nil, err
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}
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if _, err := t.CopyOutBytes(valueAddr, []byte(value)); err != nil {
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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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func getXattrFromPath(t *kernel.Task, args arch.SyscallArguments, resolveSymlink bool) (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 := uint64(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, resolveSymlink, func(root *fs.Dirent, d *fs.Dirent, _ uint) 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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n, value, err := getXattr(t, d, nameAddr, size)
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valueLen = n
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if err != nil {
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return err
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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(2) from the given *fs.Dirent.
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func getXattr(t *kernel.Task, d *fs.Dirent, nameAddr usermem.Addr, size uint64) (int, string, error) {
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if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Read: true}); err != nil {
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return 0, "", 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 0, "", err
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}
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// TODO(b/148380782): Support xattrs in namespaces other than "user".
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if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
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return 0, "", syserror.EOPNOTSUPP
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}
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// If getxattr(2) is called with size 0, the size of the value will be
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// returned successfully even if it is nonzero. In that case, we need to
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// retrieve the entire attribute value so we can return the correct size.
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requestedSize := size
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if size == 0 || size > linux.XATTR_SIZE_MAX {
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requestedSize = linux.XATTR_SIZE_MAX
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}
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value, err := d.Inode.GetXattr(t, name, requestedSize)
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if err != nil {
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return 0, "", err
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}
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n := len(value)
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if uint64(n) > requestedSize {
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return 0, "", syserror.ERANGE
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}
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// Don't copy out the attribute value if size is 0.
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if size == 0 {
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return n, "", nil
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}
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return n, value, nil
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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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return setXattrFromPath(t, args, true)
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}
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// LSetXattr implements linux syscall lsetxattr(2).
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func LSetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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return setXattrFromPath(t, args, false)
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}
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// FSetXattr implements linux syscall fsetxattr(2).
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func FSetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
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fd := args[0].Int()
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nameAddr := args[1].Pointer()
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valueAddr := args[2].Pointer()
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size := uint64(args[3].SizeT())
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flags := args[4].Uint()
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// TODO(b/113957122): Return EBADF if the fd was opened with O_PATH.
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f := t.GetFile(fd)
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if f == nil {
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return 0, nil, syserror.EBADF
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}
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defer f.DecRef()
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return 0, nil, setXattr(t, f.Dirent, nameAddr, valueAddr, uint64(size), flags)
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}
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func setXattrFromPath(t *kernel.Task, args arch.SyscallArguments, resolveSymlink bool) (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 := uint64(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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return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, resolveSymlink, func(root *fs.Dirent, d *fs.Dirent, _ uint) 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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return setXattr(t, d, nameAddr, valueAddr, uint64(size), flags)
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})
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}
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// setXattr implements setxattr(2) from the given *fs.Dirent.
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func setXattr(t *kernel.Task, d *fs.Dirent, nameAddr, valueAddr usermem.Addr, size uint64, flags uint32) error {
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if flags&^(linux.XATTR_CREATE|linux.XATTR_REPLACE) != 0 {
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return syserror.EINVAL
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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(t, d, name, value, flags)
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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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