1 files changed, 241 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/sys_xattr.go b/pkg/sentry/syscalls/linux/sys_xattr.go
new file mode 100644
index 000000000..e35c077d6
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_xattr.go
@@ -0,0 +1,241 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package linux
+
+import (
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// GetXattr implements linux syscall getxattr(2).
+func GetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return getXattrFromPath(t, args, true)
+}
+
+// LGetXattr implements linux syscall lgetxattr(2).
+func LGetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return getXattrFromPath(t, args, false)
+}
+
+// FGetXattr implements linux syscall fgetxattr(2).
+func FGetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := uint64(args[3].SizeT())
+
+	// TODO(b/113957122): Return EBADF if the fd was opened with O_PATH.
+	f := t.GetFile(fd)
+	if f == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer f.DecRef()
+
+	n, value, err := getXattr(t, f.Dirent, nameAddr, size)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	if _, err := t.CopyOutBytes(valueAddr, []byte(value)); err != nil {
+		return 0, nil, err
+	}
+	return uintptr(n), nil, nil
+}
+
+func getXattrFromPath(t *kernel.Task, args arch.SyscallArguments, resolveSymlink bool) (uintptr, *kernel.SyscallControl, error) {
+	pathAddr := args[0].Pointer()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := uint64(args[3].SizeT())
+
+	path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	valueLen := 0
+	err = fileOpOn(t, linux.AT_FDCWD, path, resolveSymlink, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
+		if dirPath && !fs.IsDir(d.Inode.StableAttr) {
+			return syserror.ENOTDIR
+		}
+
+		n, value, err := getXattr(t, d, nameAddr, size)
+		valueLen = n
+		if err != nil {
+			return err
+		}
+
+		_, err = t.CopyOutBytes(valueAddr, []byte(value))
+		return err
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+	return uintptr(valueLen), nil, nil
+}
+
+// getXattr implements getxattr(2) from the given *fs.Dirent.
+func getXattr(t *kernel.Task, d *fs.Dirent, nameAddr usermem.Addr, size uint64) (int, string, error) {
+	if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Read: true}); err != nil {
+		return 0, "", err
+	}
+
+	name, err := copyInXattrName(t, nameAddr)
+	if err != nil {
+		return 0, "", err
+	}
+
+	if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
+		return 0, "", syserror.EOPNOTSUPP
+	}
+
+	// If getxattr(2) is called with size 0, the size of the value will be
+	// returned successfully even if it is nonzero. In that case, we need to
+	// retrieve the entire attribute value so we can return the correct size.
+	requestedSize := size
+	if size == 0 || size > linux.XATTR_SIZE_MAX {
+		requestedSize = linux.XATTR_SIZE_MAX
+	}
+
+	value, err := d.Inode.GetXattr(t, name, requestedSize)
+	if err != nil {
+		return 0, "", err
+	}
+	n := len(value)
+	if uint64(n) > requestedSize {
+		return 0, "", syserror.ERANGE
+	}
+
+	// Don't copy out the attribute value if size is 0.
+	if size == 0 {
+		return n, "", nil
+	}
+	return n, value, nil
+}
+
+// SetXattr implements linux syscall setxattr(2).
+func SetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return setXattrFromPath(t, args, true)
+}
+
+// LSetXattr implements linux syscall lsetxattr(2).
+func LSetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return setXattrFromPath(t, args, false)
+}
+
+// FSetXattr implements linux syscall fsetxattr(2).
+func FSetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := uint64(args[3].SizeT())
+	flags := args[4].Uint()
+
+	// TODO(b/113957122): Return EBADF if the fd was opened with O_PATH.
+	f := t.GetFile(fd)
+	if f == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer f.DecRef()
+
+	return 0, nil, setXattr(t, f.Dirent, nameAddr, valueAddr, uint64(size), flags)
+}
+
+func setXattrFromPath(t *kernel.Task, args arch.SyscallArguments, resolveSymlink bool) (uintptr, *kernel.SyscallControl, error) {
+	pathAddr := args[0].Pointer()
+	nameAddr := args[1].Pointer()
+	valueAddr := args[2].Pointer()
+	size := uint64(args[3].SizeT())
+	flags := args[4].Uint()
+
+	path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, resolveSymlink, func(root *fs.Dirent, d *fs.Dirent, _ uint) error {
+		if dirPath && !fs.IsDir(d.Inode.StableAttr) {
+			return syserror.ENOTDIR
+		}
+
+		return setXattr(t, d, nameAddr, valueAddr, uint64(size), flags)
+	})
+}
+
+// setXattr implements setxattr(2) from the given *fs.Dirent.
+func setXattr(t *kernel.Task, d *fs.Dirent, nameAddr, valueAddr usermem.Addr, size uint64, flags uint32) error {
+	if flags&^(linux.XATTR_CREATE|linux.XATTR_REPLACE) != 0 {
+		return syserror.EINVAL
+	}
+
+	if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Write: true}); err != nil {
+		return err
+	}
+
+	name, err := copyInXattrName(t, nameAddr)
+	if err != nil {
+		return err
+	}
+
+	if size > linux.XATTR_SIZE_MAX {
+		return syserror.E2BIG
+	}
+	buf := make([]byte, size)
+	if _, err := t.CopyInBytes(valueAddr, buf); err != nil {
+		return err
+	}
+	value := string(buf)
+
+	if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
+		return syserror.EOPNOTSUPP
+	}
+
+	return d.Inode.SetXattr(t, d, name, value, flags)
+}
+
+func copyInXattrName(t *kernel.Task, nameAddr usermem.Addr) (string, error) {
+	name, err := t.CopyInString(nameAddr, linux.XATTR_NAME_MAX+1)
+	if err != nil {
+		if err == syserror.ENAMETOOLONG {
+			return "", syserror.ERANGE
+		}
+		return "", err
+	}
+	if len(name) == 0 {
+		return "", syserror.ERANGE
+	}
+	return name, nil
+}
+
+func checkXattrPermissions(t *kernel.Task, i *fs.Inode, perms fs.PermMask) error {
+	// Restrict xattrs to regular files and directories.
+	//
+	// In Linux, this restriction technically only applies to xattrs in the
+	// "user.*" namespace, but we don't allow any other xattr prefixes anyway.
+	if !fs.IsRegular(i.StableAttr) && !fs.IsDir(i.StableAttr) {
+		if perms.Write {
+			return syserror.EPERM
+		}
+		return syserror.ENODATA
+	}
+
+	return i.CheckPermission(t, perms)
+}