Merge "libprocessgroup: restrict SetupCgroups to one-time usage and only by init" am: 81cfeb54fc am: f5b778131b
am: bb07f38278
Change-Id: Id82e8ba93ba63e1fc0eb281531e062f32743f63e
diff --git a/init/init.cpp b/init/init.cpp
index a5f4549..cdec41c 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -357,7 +357,7 @@
static Result<Success> SetupCgroupsAction(const BuiltinArguments&) {
// Have to create <CGROUPS_RC_DIR> using make_dir function
// for appropriate sepolicy to be set for it
- make_dir(CGROUPS_RC_DIR, 0711);
+ make_dir(android::base::Dirname(CGROUPS_RC_PATH), 0711);
if (!CgroupSetupCgroups()) {
return ErrnoError() << "Failed to setup cgroups";
}
diff --git a/libprocessgroup/cgroup_map.cpp b/libprocessgroup/cgroup_map.cpp
index b3b497f..1e66fa4 100644
--- a/libprocessgroup/cgroup_map.cpp
+++ b/libprocessgroup/cgroup_map.cpp
@@ -227,13 +227,16 @@
#endif
+// WARNING: This function should be called only from SetupCgroups and only once.
+// It intentionally leaks an FD, so additional invocation will result in additional leak.
static bool WriteRcFile(const std::map<std::string, CgroupDescriptor>& descriptors) {
- std::string cgroup_rc_path = StringPrintf("%s/%s", CGROUPS_RC_DIR, CgroupMap::CGROUPS_RC_FILE);
- unique_fd fd(TEMP_FAILURE_RETRY(open(cgroup_rc_path.c_str(),
- O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC,
- S_IRUSR | S_IRGRP | S_IROTH)));
+ // WARNING: We are intentionally leaking the FD to keep the file open forever.
+ // Let init keep the FD open to prevent file mappings from becoming invalid in
+ // case the file gets deleted somehow.
+ int fd = TEMP_FAILURE_RETRY(open(CGROUPS_RC_PATH, O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC,
+ S_IRUSR | S_IRGRP | S_IROTH));
if (fd < 0) {
- PLOG(ERROR) << "open() failed for " << cgroup_rc_path;
+ PLOG(ERROR) << "open() failed for " << CGROUPS_RC_PATH;
return false;
}
@@ -242,14 +245,14 @@
fl.controller_count_ = descriptors.size();
int ret = TEMP_FAILURE_RETRY(write(fd, &fl, sizeof(fl)));
if (ret < 0) {
- PLOG(ERROR) << "write() failed for " << cgroup_rc_path;
+ PLOG(ERROR) << "write() failed for " << CGROUPS_RC_PATH;
return false;
}
for (const auto& [name, descriptor] : descriptors) {
ret = TEMP_FAILURE_RETRY(write(fd, descriptor.controller(), sizeof(CgroupController)));
if (ret < 0) {
- PLOG(ERROR) << "write() failed for " << cgroup_rc_path;
+ PLOG(ERROR) << "write() failed for " << CGROUPS_RC_PATH;
return false;
}
}
@@ -350,38 +353,37 @@
return true;
}
- std::string cgroup_rc_path = StringPrintf("%s/%s", CGROUPS_RC_DIR, CGROUPS_RC_FILE);
- unique_fd fd(TEMP_FAILURE_RETRY(open(cgroup_rc_path.c_str(), O_RDONLY | O_CLOEXEC)));
+ unique_fd fd(TEMP_FAILURE_RETRY(open(CGROUPS_RC_PATH, O_RDONLY | O_CLOEXEC)));
if (fd < 0) {
- PLOG(ERROR) << "open() failed for " << cgroup_rc_path;
+ PLOG(ERROR) << "open() failed for " << CGROUPS_RC_PATH;
return false;
}
if (fstat(fd, &sb) < 0) {
- PLOG(ERROR) << "fstat() failed for " << cgroup_rc_path;
+ PLOG(ERROR) << "fstat() failed for " << CGROUPS_RC_PATH;
return false;
}
size_t file_size = sb.st_size;
if (file_size < sizeof(CgroupFile)) {
- LOG(ERROR) << "Invalid file format " << cgroup_rc_path;
+ LOG(ERROR) << "Invalid file format " << CGROUPS_RC_PATH;
return false;
}
CgroupFile* file_data = (CgroupFile*)mmap(nullptr, file_size, PROT_READ, MAP_SHARED, fd, 0);
if (file_data == MAP_FAILED) {
- PLOG(ERROR) << "Failed to mmap " << cgroup_rc_path;
+ PLOG(ERROR) << "Failed to mmap " << CGROUPS_RC_PATH;
return false;
}
if (file_data->version_ != CgroupFile::FILE_CURR_VERSION) {
- LOG(ERROR) << cgroup_rc_path << " file version mismatch";
+ LOG(ERROR) << CGROUPS_RC_PATH << " file version mismatch";
munmap(file_data, file_size);
return false;
}
if (file_size != sizeof(CgroupFile) + file_data->controller_count_ * sizeof(CgroupController)) {
- LOG(ERROR) << cgroup_rc_path << " file has invalid size";
+ LOG(ERROR) << CGROUPS_RC_PATH << " file has invalid size";
munmap(file_data, file_size);
return false;
}
@@ -412,6 +414,18 @@
bool CgroupMap::SetupCgroups() {
std::map<std::string, CgroupDescriptor> descriptors;
+ if (getpid() != 1) {
+ LOG(ERROR) << "Cgroup setup can be done only by init process";
+ return false;
+ }
+
+ // Make sure we do this only one time. No need for std::call_once because
+ // init is a single-threaded process
+ if (access(CGROUPS_RC_PATH, F_OK) == 0) {
+ LOG(WARNING) << "Attempt to call SetupCgroups more than once";
+ return true;
+ }
+
// load cgroups.json file
if (!ReadDescriptors(&descriptors)) {
LOG(ERROR) << "Failed to load cgroup description file";
@@ -428,8 +442,8 @@
}
// mkdir <CGROUPS_RC_DIR> 0711 system system
- if (!Mkdir(CGROUPS_RC_DIR, 0711, "system", "system")) {
- LOG(ERROR) << "Failed to create directory for <CGROUPS_RC_FILE> file";
+ if (!Mkdir(android::base::Dirname(CGROUPS_RC_PATH), 0711, "system", "system")) {
+ LOG(ERROR) << "Failed to create directory for " << CGROUPS_RC_PATH << " file";
return false;
}
@@ -438,13 +452,12 @@
// and limits infrormation shared with unprivileged processes
// to the minimum subset of information from cgroups.json
if (!WriteRcFile(descriptors)) {
- LOG(ERROR) << "Failed to write " << CGROUPS_RC_FILE << " file";
+ LOG(ERROR) << "Failed to write " << CGROUPS_RC_PATH << " file";
return false;
}
- std::string cgroup_rc_path = StringPrintf("%s/%s", CGROUPS_RC_DIR, CGROUPS_RC_FILE);
- // chmod 0644 <cgroup_rc_path>
- if (fchmodat(AT_FDCWD, cgroup_rc_path.c_str(), 0644, AT_SYMLINK_NOFOLLOW) < 0) {
+ // chmod 0644 <CGROUPS_RC_PATH>
+ if (fchmodat(AT_FDCWD, CGROUPS_RC_PATH, 0644, AT_SYMLINK_NOFOLLOW) < 0) {
PLOG(ERROR) << "fchmodat() failed";
return false;
}
diff --git a/libprocessgroup/cgroup_map.h b/libprocessgroup/cgroup_map.h
index 1c355cd..304ae15 100644
--- a/libprocessgroup/cgroup_map.h
+++ b/libprocessgroup/cgroup_map.h
@@ -75,8 +75,6 @@
class CgroupMap {
public:
- static constexpr const char* CGROUPS_RC_FILE = "cgroup.rc";
-
// Selinux policy ensures only init process can successfully use this function
static bool SetupCgroups();
diff --git a/libprocessgroup/include/processgroup/processgroup.h b/libprocessgroup/include/processgroup/processgroup.h
index 6f973b8..46b8676 100644
--- a/libprocessgroup/include/processgroup/processgroup.h
+++ b/libprocessgroup/include/processgroup/processgroup.h
@@ -24,7 +24,7 @@
__BEGIN_DECLS
static constexpr const char* CGROUPV2_CONTROLLER_NAME = "cgroup2";
-static constexpr const char* CGROUPS_RC_DIR = "/dev/cgroup_info";
+static constexpr const char* CGROUPS_RC_PATH = "/dev/cgroup_info/cgroup.rc";
bool CgroupSetupCgroups();
bool CgroupGetControllerPath(const std::string& cgroup_name, std::string* path);