80 lines
2.8 KiB
C++
80 lines
2.8 KiB
C++
// Copyright 2018 Google LLC
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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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#include "test/util/capability_util.h"
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#include <linux/capability.h>
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#include <sched.h>
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#include <sys/mman.h>
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#include <sys/wait.h>
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#include "absl/strings/str_cat.h"
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#include "test/util/memory_util.h"
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#include "test/util/posix_error.h"
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#include "test/util/save_util.h"
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#include "test/util/test_util.h"
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namespace gvisor {
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namespace testing {
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PosixErrorOr<bool> CanCreateUserNamespace() {
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// The most reliable way to determine if userns creation is possible is by
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// trying to create one; see below.
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ASSIGN_OR_RETURN_ERRNO(
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auto child_stack,
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MmapAnon(kPageSize, PROT_READ | PROT_WRITE, MAP_PRIVATE));
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int const child_pid =
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clone(+[](void*) { return 0; },
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reinterpret_cast<void*>(child_stack.addr() + kPageSize),
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CLONE_NEWUSER | SIGCHLD, /* arg = */ nullptr);
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if (child_pid > 0) {
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int status;
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int const ret = waitpid(child_pid, &status, /* options = */ 0);
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MaybeSave();
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if (ret < 0) {
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return PosixError(errno, "waitpid");
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}
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if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
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return PosixError(
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ESRCH, absl::StrCat("child process exited with status ", status));
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}
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return true;
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} else if (errno == EPERM) {
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// Per clone(2), EPERM can be returned if:
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//
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// - "CLONE_NEWUSER was specified in flags, but either the effective user ID
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// or the effective group ID of the caller does not have a mapping in the
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// parent namespace (see user_namespaces(7))."
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//
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// - "(since Linux 3.9) CLONE_NEWUSER was specified in flags and the caller
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// is in a chroot environment (i.e., the caller's root directory does
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// not match the root directory of the mount namespace in which it
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// resides)."
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LOG(INFO) << "clone(CLONE_NEWUSER) failed with EPERM";
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return false;
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} else if (errno == EUSERS) {
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// "(since Linux 3.11) CLONE_NEWUSER was specified in flags, and the call
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// would cause the limit on the number of nested user namespaces to be
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// exceeded. See user_namespaces(7)."
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LOG(INFO) << "clone(CLONE_NEWUSER) failed with EUSERS";
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return false;
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} else {
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// Unexpected error code; indicate an actual error.
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return PosixError(errno, "clone(CLONE_NEWUSER)");
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}
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}
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} // namespace testing
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} // namespace gvisor
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