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// Copyright 2019 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "brillo/scoped_mount_namespace.h"
#include <fcntl.h>
#include <sched.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <string>
#include <utility>
#include <base/posix/eintr_wrapper.h>
#include <base/strings/stringprintf.h>
namespace {
constexpr char kCurrentMountNamespacePath[] = "/proc/self/ns/mnt";
} // anonymous namespace
namespace brillo {
ScopedMountNamespace::ScopedMountNamespace(base::ScopedFD mount_namespace_fd)
: mount_namespace_fd_(std::move(mount_namespace_fd)) {}
ScopedMountNamespace::~ScopedMountNamespace() {
PLOG_IF(ERROR, setns(mount_namespace_fd_.get(), CLONE_NEWNS) != 0)
<< "Ignoring failure to restore original mount namespace";
}
// static
std::unique_ptr<ScopedMountNamespace> ScopedMountNamespace::CreateForPid(
pid_t pid) {
std::string ns_path = base::StringPrintf("/proc/%d/ns/mnt", pid);
return CreateFromPath(base::FilePath(ns_path));
}
// static
std::unique_ptr<ScopedMountNamespace> ScopedMountNamespace::CreateFromPath(
base::FilePath ns_path) {
base::ScopedFD original_mount_namespace_fd(
HANDLE_EINTR(open(kCurrentMountNamespacePath, O_RDONLY)));
if (!original_mount_namespace_fd.is_valid()) {
PLOG(ERROR) << "Failed to open original mount namespace FD at "
<< kCurrentMountNamespacePath;
return nullptr;
}
base::ScopedFD mount_namespace_fd(
HANDLE_EINTR(open(ns_path.value().c_str(), O_RDONLY)));
if (!mount_namespace_fd.is_valid()) {
PLOG(ERROR) << "Failed to open mount namespace FD at " << ns_path.value();
return nullptr;
}
if (setns(mount_namespace_fd.get(), CLONE_NEWNS) != 0) {
PLOG(ERROR) << "Failed to enter mount namespace at " << ns_path.value();
return nullptr;
}
return std::make_unique<ScopedMountNamespace>(
std::move(original_mount_namespace_fd));
}
} // namespace brillo
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