From e6f4124afd951c3b089f9c75c499c14f4d90a590 Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Mon, 16 Dec 2019 13:18:36 -0800 Subject: 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 --- pkg/abi/linux/BUILD | 1 + pkg/abi/linux/xattr.go | 27 +++++ pkg/sentry/fs/inode.go | 8 ++ pkg/sentry/fs/inode_overlay.go | 5 + pkg/sentry/syscalls/linux/BUILD | 1 + pkg/sentry/syscalls/linux/linux64_amd64.go | 4 +- pkg/sentry/syscalls/linux/linux64_arm64.go | 4 +- pkg/sentry/syscalls/linux/sys_xattr.go | 169 +++++++++++++++++++++++++++++ test/syscalls/linux/xattr.cc | 79 +++++++------- 9 files changed, 253 insertions(+), 45 deletions(-) create mode 100644 pkg/abi/linux/xattr.go create mode 100644 pkg/sentry/syscalls/linux/sys_xattr.go 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) +) diff --git a/pkg/sentry/fs/inode.go b/pkg/sentry/fs/inode.go index 2d43dff1d..91e2fde2f 100644 --- a/pkg/sentry/fs/inode.go +++ b/pkg/sentry/fs/inode.go @@ -270,6 +270,14 @@ func (i *Inode) Getxattr(name string) (string, error) { return i.InodeOperations.Getxattr(i, name) } +// Setxattr calls i.InodeOperations.Setxattr with i as the Inode. +func (i *Inode) Setxattr(name, value string) error { + if i.overlay != nil { + return overlaySetxattr(i.overlay, name, value) + } + return i.InodeOperations.Setxattr(i, name, value) +} + // Listxattr calls i.InodeOperations.Listxattr with i as the Inode. func (i *Inode) Listxattr() (map[string]struct{}, error) { if i.overlay != nil { diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go index a09147080..63a991beb 100644 --- a/pkg/sentry/fs/inode_overlay.go +++ b/pkg/sentry/fs/inode_overlay.go @@ -552,6 +552,11 @@ func overlayGetxattr(o *overlayEntry, name string) (string, error) { return s, err } +// TODO(b/146028302): Support setxattr for overlayfs. +func overlaySetxattr(o *overlayEntry, name, value string) error { + return syserror.EOPNOTSUPP +} + func overlayListxattr(o *overlayEntry) (map[string]struct{}, error) { o.copyMu.RLock() defer o.copyMu.RUnlock() diff --git a/pkg/sentry/syscalls/linux/BUILD b/pkg/sentry/syscalls/linux/BUILD index 4c0bf96e4..6766ba587 100644 --- a/pkg/sentry/syscalls/linux/BUILD +++ b/pkg/sentry/syscalls/linux/BUILD @@ -49,6 +49,7 @@ go_library( "sys_tls.go", "sys_utsname.go", "sys_write.go", + "sys_xattr.go", "timespec.go", ], importpath = "gvisor.dev/gvisor/pkg/sentry/syscalls/linux", diff --git a/pkg/sentry/syscalls/linux/linux64_amd64.go b/pkg/sentry/syscalls/linux/linux64_amd64.go index 797542d28..272ae9991 100644 --- a/pkg/sentry/syscalls/linux/linux64_amd64.go +++ b/pkg/sentry/syscalls/linux/linux64_amd64.go @@ -228,10 +228,10 @@ var AMD64 = &kernel.SyscallTable{ 185: syscalls.Error("security", syserror.ENOSYS, "Not implemented in Linux.", nil), 186: syscalls.Supported("gettid", Gettid), 187: syscalls.Supported("readahead", Readahead), - 188: syscalls.Error("setxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), + 188: syscalls.PartiallySupported("setxattr", Setxattr, "Only supported for tmpfs.", nil), 189: syscalls.Error("lsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 190: syscalls.Error("fsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), - 191: syscalls.ErrorWithEvent("getxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), + 191: syscalls.PartiallySupported("getxattr", Getxattr, "Only supported for tmpfs.", nil), 192: syscalls.ErrorWithEvent("lgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 193: syscalls.ErrorWithEvent("fgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 194: syscalls.ErrorWithEvent("listxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), diff --git a/pkg/sentry/syscalls/linux/linux64_arm64.go b/pkg/sentry/syscalls/linux/linux64_arm64.go index 2bc7faff5..3b584eed9 100644 --- a/pkg/sentry/syscalls/linux/linux64_arm64.go +++ b/pkg/sentry/syscalls/linux/linux64_arm64.go @@ -41,10 +41,10 @@ var ARM64 = &kernel.SyscallTable{ 2: syscalls.PartiallySupported("io_submit", IoSubmit, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}), 3: syscalls.PartiallySupported("io_cancel", IoCancel, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}), 4: syscalls.PartiallySupported("io_getevents", IoGetevents, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}), - 5: syscalls.Error("setxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), + 5: syscalls.PartiallySupported("setxattr", Setxattr, "Only supported for tmpfs.", nil), 6: syscalls.Error("lsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 7: syscalls.Error("fsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), - 8: syscalls.ErrorWithEvent("getxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), + 8: syscalls.PartiallySupported("getxattr", Getxattr, "Only supported for tmpfs.", nil), 9: syscalls.ErrorWithEvent("lgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 10: syscalls.ErrorWithEvent("fgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 11: syscalls.ErrorWithEvent("listxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), diff --git a/pkg/sentry/syscalls/linux/sys_xattr.go b/pkg/sentry/syscalls/linux/sys_xattr.go new file mode 100644 index 000000000..97d9a65ea --- /dev/null +++ b/pkg/sentry/syscalls/linux/sys_xattr.go @@ -0,0 +1,169 @@ +// 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) { + pathAddr := args[0].Pointer() + nameAddr := args[1].Pointer() + valueAddr := args[2].Pointer() + size := 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, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error { + value, err := getxattr(t, d, dirPath, nameAddr) + if err != nil { + return err + } + + valueLen = len(value) + if size == 0 { + return nil + } + if size > linux.XATTR_SIZE_MAX { + size = linux.XATTR_SIZE_MAX + } + if valueLen > int(size) { + return syserror.ERANGE + } + + _, err = t.CopyOutBytes(valueAddr, []byte(value)) + return err + }) + if err != nil { + return 0, nil, err + } + return uintptr(valueLen), nil, nil +} + +// getxattr implements getxattr from the given *fs.Dirent. +func getxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr usermem.Addr) (string, error) { + if dirPath && !fs.IsDir(d.Inode.StableAttr) { + return "", syserror.ENOTDIR + } + + if err := checkXattrPermissions(t, d.Inode, fs.PermMask{Read: true}); err != nil { + return "", err + } + + name, err := copyInXattrName(t, nameAddr) + if err != nil { + return "", err + } + + if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) { + return "", syserror.EOPNOTSUPP + } + + return d.Inode.Getxattr(name) +} + +// Setxattr implements linux syscall setxattr(2). +func Setxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { + pathAddr := args[0].Pointer() + nameAddr := args[1].Pointer() + valueAddr := args[2].Pointer() + size := args[3].SizeT() + flags := args[4].Uint() + + path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */) + if err != nil { + return 0, nil, err + } + + if flags&^(linux.XATTR_CREATE|linux.XATTR_REPLACE) != 0 { + return 0, nil, syserror.EINVAL + } + + return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error { + return setxattr(t, d, dirPath, nameAddr, valueAddr, size, flags) + }) +} + +// setxattr implements setxattr from the given *fs.Dirent. +func setxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr usermem.Addr, size uint, flags uint32) error { + if dirPath && !fs.IsDir(d.Inode.StableAttr) { + return syserror.ENOTDIR + } + + 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(name, value) +} + +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) +} diff --git a/test/syscalls/linux/xattr.cc b/test/syscalls/linux/xattr.cc index 3e07b634b..75740238c 100644 --- a/test/syscalls/linux/xattr.cc +++ b/test/syscalls/linux/xattr.cc @@ -28,6 +28,7 @@ #include "test/util/capability_util.h" #include "test/util/posix_error.h" #include "test/util/temp_path.h" +#include "test/util/test_util.h" namespace gvisor { namespace testing { @@ -37,9 +38,6 @@ namespace { class XattrTest : public FileTest {}; TEST_F(XattrTest, XattrNullName) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - const char* path = test_file_name_.c_str(); EXPECT_THAT(setxattr(path, nullptr, nullptr, 0, /*flags=*/0), @@ -49,9 +47,6 @@ TEST_F(XattrTest, XattrNullName) { } TEST_F(XattrTest, XattrEmptyName) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - const char* path = test_file_name_.c_str(); EXPECT_THAT(setxattr(path, "", nullptr, 0, /*flags=*/0), @@ -60,16 +55,17 @@ TEST_F(XattrTest, XattrEmptyName) { } TEST_F(XattrTest, XattrLargeName) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - const char* path = test_file_name_.c_str(); std::string name = "user."; name += std::string(XATTR_NAME_MAX - name.length(), 'a'); - EXPECT_THAT(setxattr(path, name.c_str(), nullptr, 0, /*flags=*/0), - SyscallSucceeds()); - EXPECT_THAT(getxattr(path, name.c_str(), nullptr, 0), - SyscallSucceedsWithValue(0)); + + // TODO(b/127675828): Support setxattr and getxattr. + if (!IsRunningOnGvisor()) { + EXPECT_THAT(setxattr(path, name.c_str(), nullptr, 0, /*flags=*/0), + SyscallSucceeds()); + EXPECT_THAT(getxattr(path, name.c_str(), nullptr, 0), + SyscallSucceedsWithValue(0)); + } name += "a"; EXPECT_THAT(setxattr(path, name.c_str(), nullptr, 0, /*flags=*/0), @@ -79,9 +75,6 @@ TEST_F(XattrTest, XattrLargeName) { } TEST_F(XattrTest, XattrInvalidPrefix) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - const char* path = test_file_name_.c_str(); std::string name(XATTR_NAME_MAX, 'a'); EXPECT_THAT(setxattr(path, name.c_str(), nullptr, 0, /*flags=*/0), @@ -91,9 +84,6 @@ TEST_F(XattrTest, XattrInvalidPrefix) { } TEST_F(XattrTest, XattrReadOnly) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - // Drop capabilities that allow us to override file and directory permissions. ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false)); ASSERT_NO_ERRNO(SetCapability(CAP_DAC_READ_SEARCH, false)); @@ -102,22 +92,28 @@ TEST_F(XattrTest, XattrReadOnly) { char name[] = "user.abc"; char val = 'a'; size_t size = sizeof(val); - EXPECT_THAT(setxattr(path, name, &val, size, /*flags=*/0), SyscallSucceeds()); + + // TODO(b/127675828): Support setxattr and getxattr. + if (!IsRunningOnGvisor()) { + EXPECT_THAT(setxattr(path, name, &val, size, /*flags=*/0), + SyscallSucceeds()); + } ASSERT_NO_ERRNO(testing::Chmod(test_file_name_, S_IRUSR)); EXPECT_THAT(setxattr(path, name, &val, size, /*flags=*/0), SyscallFailsWithErrno(EACCES)); - char buf = '-'; - EXPECT_THAT(getxattr(path, name, &buf, size), SyscallSucceedsWithValue(size)); - EXPECT_EQ(buf, val); + // TODO(b/127675828): Support setxattr and getxattr. + if (!IsRunningOnGvisor()) { + char buf = '-'; + EXPECT_THAT(getxattr(path, name, &buf, size), + SyscallSucceedsWithValue(size)); + EXPECT_EQ(buf, val); + } } TEST_F(XattrTest, XattrWriteOnly) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - // Drop capabilities that allow us to override file and directory permissions. ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false)); ASSERT_NO_ERRNO(SetCapability(CAP_DAC_READ_SEARCH, false)); @@ -128,7 +124,12 @@ TEST_F(XattrTest, XattrWriteOnly) { char name[] = "user.abc"; char val = 'a'; size_t size = sizeof(val); - EXPECT_THAT(setxattr(path, name, &val, size, /*flags=*/0), SyscallSucceeds()); + + // TODO(b/127675828): Support setxattr and getxattr. + if (!IsRunningOnGvisor()) { + EXPECT_THAT(setxattr(path, name, &val, size, /*flags=*/0), + SyscallSucceeds()); + } EXPECT_THAT(getxattr(path, name, nullptr, 0), SyscallFailsWithErrno(EACCES)); } @@ -172,9 +173,6 @@ TEST_F(XattrTest, XattrOnSymlink) { } TEST_F(XattrTest, XattrOnInvalidFileTypes) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - char name[] = "user.abc"; char char_device[] = "/dev/zero"; @@ -226,9 +224,6 @@ TEST_F(XattrTest, SetxattrZeroSize) { } TEST_F(XattrTest, SetxattrSizeTooLarge) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - const char* path = test_file_name_.c_str(); char name[] = "user.abc"; @@ -240,19 +235,24 @@ TEST_F(XattrTest, SetxattrSizeTooLarge) { EXPECT_THAT(setxattr(path, name, val.data(), size, /*flags=*/0), SyscallFailsWithErrno(E2BIG)); - EXPECT_THAT(getxattr(path, name, nullptr, 0), SyscallFailsWithErrno(ENODATA)); + // TODO(b/127675828): Support setxattr and getxattr. + if (!IsRunningOnGvisor()) { + EXPECT_THAT(getxattr(path, name, nullptr, 0), + SyscallFailsWithErrno(ENODATA)); + } } TEST_F(XattrTest, SetxattrNullValueAndNonzeroSize) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - const char* path = test_file_name_.c_str(); char name[] = "user.abc"; EXPECT_THAT(setxattr(path, name, nullptr, 1, /*flags=*/0), SyscallFailsWithErrno(EFAULT)); - EXPECT_THAT(getxattr(path, name, nullptr, 0), SyscallFailsWithErrno(ENODATA)); + // TODO(b/127675828): Support setxattr and getxattr. + if (!IsRunningOnGvisor()) { + EXPECT_THAT(getxattr(path, name, nullptr, 0), + SyscallFailsWithErrno(ENODATA)); + } } TEST_F(XattrTest, SetxattrNullValueAndZeroSize) { @@ -350,9 +350,6 @@ TEST_F(XattrTest, SetxattrReplaceFlag) { } TEST_F(XattrTest, SetxattrInvalidFlags) { - // TODO(b/127675828): Support setxattr and getxattr. - SKIP_IF(IsRunningOnGvisor()); - const char* path = test_file_name_.c_str(); int invalid_flags = 0xff; EXPECT_THAT(setxattr(path, nullptr, nullptr, 0, invalid_flags), -- cgit v1.2.3