Implement checks for get/setxattr at the syscall layer.

Add checks for input arguments, file type, permissions, etc. that match
the Linux implementation. A call to get/setxattr that passes all the
checks will still currently return EOPNOTSUPP. Actual support will be
added in following commits.

Only allow user.* extended attributes for the time being.

PiperOrigin-RevId: 285835159

2 files changed, 28 insertions, 0 deletions

diff --git a/pkg/abi/linux/BUILD b/pkg/abi/linux/BUILD
index 51774c6b6..9553f164d 100644
--- a/pkg/abi/linux/BUILD
+++ b/pkg/abi/linux/BUILD
@@ -57,6 +57,7 @@ go_library(
         "uio.go",
         "utsname.go",
         "wait.go",
+        "xattr.go",
     ],
     importpath = "gvisor.dev/gvisor/pkg/abi/linux",
     visibility = ["//visibility:public"],
diff --git a/pkg/abi/linux/xattr.go b/pkg/abi/linux/xattr.go
new file mode 100644
index 000000000..a3b6406fa
--- /dev/null
+++ b/pkg/abi/linux/xattr.go
@@ -0,0 +1,27 @@
+// 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
+
+// Constants for extended attributes.
+const (
+	XATTR_NAME_MAX = 255
+	XATTR_SIZE_MAX = 65536
+
+	XATTR_CREATE  = 1
+	XATTR_REPLACE = 2
+
+	XATTR_USER_PREFIX     = "user."
+	XATTR_USER_PREFIX_LEN = len(XATTR_USER_PREFIX)
+)