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platform_system_core/libprocessgroup/processgroup.cpp

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/*
* Copyright 2014 Google, Inc
*
* 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.
*/
//#define LOG_NDEBUG 0
#define LOG_TAG "libprocessgroup"
#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <chrono>
#include <memory>
#include <mutex>
#include <set>
#include <thread>
#include <android-base/logging.h>
#include <android-base/unique_fd.h>
#include <private/android_filesystem_config.h>
#include <processgroup/processgroup.h>
using namespace std::chrono_literals;
#define MEM_CGROUP_PATH "/dev/memcg/apps"
#define MEM_CGROUP_TASKS "/dev/memcg/apps/tasks"
#define ACCT_CGROUP_PATH "/acct"
#define PROCESSGROUP_UID_PREFIX "uid_"
#define PROCESSGROUP_PID_PREFIX "pid_"
#define PROCESSGROUP_CGROUP_PROCS_FILE "/cgroup.procs"
#define PROCESSGROUP_MAX_UID_LEN 11
#define PROCESSGROUP_MAX_PID_LEN 11
#define PROCESSGROUP_MAX_PATH_LEN \
((sizeof(MEM_CGROUP_PATH) > sizeof(ACCT_CGROUP_PATH) ? \
sizeof(MEM_CGROUP_PATH) : sizeof(ACCT_CGROUP_PATH)) + \
sizeof(PROCESSGROUP_UID_PREFIX) + 1 + \
PROCESSGROUP_MAX_UID_LEN + \
sizeof(PROCESSGROUP_PID_PREFIX) + 1 + \
PROCESSGROUP_MAX_PID_LEN + \
sizeof(PROCESSGROUP_CGROUP_PROCS_FILE) + \
1)
std::once_flag init_path_flag;
class ProcessGroup {
public:
ProcessGroup() : buf_ptr_(buf_), buf_len_(0) {}
bool Open(uid_t uid, int pid);
// Return positive number and sets *pid = next pid in process cgroup on success
// Returns 0 if there are no pids left in the process cgroup
// Returns -errno if an error was encountered
int GetOneAppProcess(pid_t* pid);
private:
// Returns positive number of bytes filled on success
// Returns 0 if there was nothing to read
// Returns -errno if an error was encountered
int RefillBuffer();
android::base::unique_fd fd_;
char buf_[128];
char* buf_ptr_;
size_t buf_len_;
};
static const char* getCgroupRootPath() {
static const char* cgroup_root_path = NULL;
std::call_once(init_path_flag, [&]() {
// Check if mem cgroup is mounted, only then check for write-access to avoid
// SELinux denials
cgroup_root_path = access(MEM_CGROUP_TASKS, F_OK) || access(MEM_CGROUP_PATH, W_OK) ?
ACCT_CGROUP_PATH : MEM_CGROUP_PATH;
});
return cgroup_root_path;
}
static int convertUidToPath(char *path, size_t size, uid_t uid)
{
return snprintf(path, size, "%s/%s%d",
getCgroupRootPath(),
PROCESSGROUP_UID_PREFIX,
uid);
}
static int convertUidPidToPath(char *path, size_t size, uid_t uid, int pid)
{
return snprintf(path, size, "%s/%s%d/%s%d",
getCgroupRootPath(),
PROCESSGROUP_UID_PREFIX,
uid,
PROCESSGROUP_PID_PREFIX,
pid);
}
bool ProcessGroup::Open(uid_t uid, int pid) {
char path[PROCESSGROUP_MAX_PATH_LEN] = {0};
convertUidPidToPath(path, sizeof(path), uid, pid);
strlcat(path, PROCESSGROUP_CGROUP_PROCS_FILE, sizeof(path));
int fd = open(path, O_RDONLY);
if (fd < 0) return false;
fd_.reset(fd);
LOG(VERBOSE) << "Initialized context for " << path;
return true;
}
int ProcessGroup::RefillBuffer() {
memmove(buf_, buf_ptr_, buf_len_);
buf_ptr_ = buf_;
ssize_t ret = read(fd_, buf_ptr_ + buf_len_, sizeof(buf_) - buf_len_ - 1);
if (ret < 0) {
return -errno;
} else if (ret == 0) {
return 0;
}
buf_len_ += ret;
buf_[buf_len_] = 0;
LOG(VERBOSE) << "Read " << ret << " to buffer: " << buf_;
assert(buf_len_ <= sizeof(buf_));
return ret;
}
int ProcessGroup::GetOneAppProcess(pid_t* out_pid) {
*out_pid = 0;
char* eptr;
while ((eptr = static_cast<char*>(memchr(buf_ptr_, '\n', buf_len_))) == nullptr) {
int ret = RefillBuffer();
if (ret <= 0) return ret;
}
*eptr = '\0';
char* pid_eptr = nullptr;
errno = 0;
long pid = strtol(buf_ptr_, &pid_eptr, 10);
if (errno != 0) {
return -errno;
}
if (pid_eptr != eptr) {
errno = EINVAL;
return -errno;
}
buf_len_ -= (eptr - buf_ptr_) + 1;
buf_ptr_ = eptr + 1;
*out_pid = static_cast<pid_t>(pid);
return 1;
}
static int removeProcessGroup(uid_t uid, int pid)
{
int ret;
char path[PROCESSGROUP_MAX_PATH_LEN] = {0};
convertUidPidToPath(path, sizeof(path), uid, pid);
ret = rmdir(path);
convertUidToPath(path, sizeof(path), uid);
rmdir(path);
return ret;
}
static void removeUidProcessGroups(const char *uid_path)
{
std::unique_ptr<DIR, decltype(&closedir)> uid(opendir(uid_path), closedir);
if (uid != NULL) {
dirent* dir;
while ((dir = readdir(uid.get())) != nullptr) {
char path[PROCESSGROUP_MAX_PATH_LEN];
if (dir->d_type != DT_DIR) {
continue;
}
if (strncmp(dir->d_name, PROCESSGROUP_PID_PREFIX, strlen(PROCESSGROUP_PID_PREFIX))) {
continue;
}
snprintf(path, sizeof(path), "%s/%s", uid_path, dir->d_name);
LOG(VERBOSE) << "Removing " << path;
if (rmdir(path) == -1) PLOG(WARNING) << "Failed to remove " << path;
}
}
}
void removeAllProcessGroups()
{
LOG(VERBOSE) << "removeAllProcessGroups()";
const char* cgroup_root_path = getCgroupRootPath();
std::unique_ptr<DIR, decltype(&closedir)> root(opendir(cgroup_root_path), closedir);
if (root == NULL) {
PLOG(ERROR) << "Failed to open " << cgroup_root_path;
} else {
dirent* dir;
while ((dir = readdir(root.get())) != nullptr) {
char path[PROCESSGROUP_MAX_PATH_LEN];
if (dir->d_type != DT_DIR) {
continue;
}
if (strncmp(dir->d_name, PROCESSGROUP_UID_PREFIX, strlen(PROCESSGROUP_UID_PREFIX))) {
continue;
}
snprintf(path, sizeof(path), "%s/%s", cgroup_root_path, dir->d_name);
removeUidProcessGroups(path);
LOG(VERBOSE) << "Removing " << path;
if (rmdir(path) == -1) PLOG(WARNING) << "Failed to remove " << path;
}
}
}
// Returns number of processes killed on success
// Returns 0 if there are no processes in the process cgroup left to kill
// Returns -errno on error
static int doKillProcessGroupOnce(uid_t uid, int initialPid, int signal) {
ProcessGroup process_group;
if (!process_group.Open(uid, initialPid)) {
PLOG(WARNING) << "Failed to open process cgroup uid " << uid << " pid " << initialPid;
return -errno;
}
// We separate all of the pids in the cgroup into those pids that are also the leaders of
// process groups (stored in the pgids set) and those that are not (stored in the pids set).
std::set<pid_t> pgids;
pgids.emplace(initialPid);
std::set<pid_t> pids;
int ret;
pid_t pid;
int processes = 0;
while ((ret = process_group.GetOneAppProcess(&pid)) > 0 && pid >= 0) {
processes++;
if (pid == 0) {
// Should never happen... but if it does, trying to kill this
// will boomerang right back and kill us! Let's not let that happen.
LOG(WARNING) << "Yikes, we've been told to kill pid 0! How about we don't do that?";
continue;
}
pid_t pgid = getpgid(pid);
if (pgid == -1) PLOG(ERROR) << "getpgid(" << pid << ") failed";
if (pgid == pid) {
pgids.emplace(pid);
} else {
pids.emplace(pid);
}
}
// Erase all pids that will be killed when we kill the process groups.
for (auto it = pids.begin(); it != pids.end();) {
pid_t pgid = getpgid(pid);
if (pgids.count(pgid) == 1) {
it = pids.erase(it);
} else {
++it;
}
}
// Kill all process groups.
for (const auto pgid : pgids) {
LOG(VERBOSE) << "Killing process group " << -pgid << " in uid " << uid
<< " as part of process cgroup " << initialPid;
if (kill(-pgid, signal) == -1) {
PLOG(WARNING) << "kill(" << -pgid << ", " << signal << ") failed";
}
}
// Kill remaining pids.
for (const auto pid : pids) {
LOG(VERBOSE) << "Killing pid " << pid << " in uid " << uid << " as part of process cgroup "
<< initialPid;
if (kill(pid, signal) == -1) {
PLOG(WARNING) << "kill(" << pid << ", " << signal << ") failed";
}
}
return ret >= 0 ? processes : ret;
}
static int killProcessGroup(uid_t uid, int initialPid, int signal, int retries) {
std::chrono::steady_clock::time_point start = std::chrono::steady_clock::now();
int retry = retries;
int processes;
while ((processes = doKillProcessGroupOnce(uid, initialPid, signal)) > 0) {
LOG(VERBOSE) << "Killed " << processes << " processes for processgroup " << initialPid;
if (retry > 0) {
std::this_thread::sleep_for(5ms);
--retry;
} else {
break;
}
}
if (processes < 0) {
PLOG(ERROR) << "Error encountered killing process cgroup uid " << uid << " pid "
<< initialPid;
return -1;
}
std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();
auto ms = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();
// We only calculate the number of 'processes' when killing the processes.
// In the retries == 0 case, we only kill the processes once and therefore
// will not have waited then recalculated how many processes are remaining
// after the first signals have been sent.
// Logging anything regarding the number of 'processes' here does not make sense.
if (processes == 0) {
if (retries > 0) {
LOG(INFO) << "Successfully killed process cgroup uid " << uid << " pid " << initialPid
<< " in " << static_cast<int>(ms) << "ms";
}
return removeProcessGroup(uid, initialPid);
} else {
if (retries > 0) {
LOG(ERROR) << "Failed to kill process cgroup uid " << uid << " pid " << initialPid
<< " in " << static_cast<int>(ms) << "ms, " << processes
<< " processes remain";
}
return -1;
}
}
int killProcessGroup(uid_t uid, int initialPid, int signal) {
return killProcessGroup(uid, initialPid, signal, 40 /*retries*/);
}
int killProcessGroupOnce(uid_t uid, int initialPid, int signal) {
return killProcessGroup(uid, initialPid, signal, 0 /*retries*/);
}
static bool mkdirAndChown(const char *path, mode_t mode, uid_t uid, gid_t gid)
{
if (mkdir(path, mode) == -1 && errno != EEXIST) {
return false;
}
if (chown(path, uid, gid) == -1) {
int saved_errno = errno;
rmdir(path);
errno = saved_errno;
return false;
}
return true;
}
int createProcessGroup(uid_t uid, int initialPid)
{
char path[PROCESSGROUP_MAX_PATH_LEN] = {0};
convertUidToPath(path, sizeof(path), uid);
if (!mkdirAndChown(path, 0750, AID_SYSTEM, AID_SYSTEM)) {
PLOG(ERROR) << "Failed to make and chown " << path;
return -errno;
}
convertUidPidToPath(path, sizeof(path), uid, initialPid);
if (!mkdirAndChown(path, 0750, AID_SYSTEM, AID_SYSTEM)) {
PLOG(ERROR) << "Failed to make and chown " << path;
return -errno;
}
strlcat(path, PROCESSGROUP_CGROUP_PROCS_FILE, sizeof(path));
int fd = open(path, O_WRONLY);
if (fd == -1) {
int ret = -errno;
PLOG(ERROR) << "Failed to open " << path;
return ret;
}
char pid[PROCESSGROUP_MAX_PID_LEN + 1] = {0};
int len = snprintf(pid, sizeof(pid), "%d", initialPid);
int ret = 0;
if (write(fd, pid, len) < 0) {
ret = -errno;
PLOG(ERROR) << "Failed to write '" << pid << "' to " << path;
}
close(fd);
return ret;
}
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