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f840c7d58dcd39fa98a887c50a9be5c35dbb599f
systemd/src/basic/process-util.c
Luca Boccassi f840c7d58d process-util: add helper to verify a pid via its pidfd
2023-01-20 12:18:05 +00:00

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <linux/oom.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/personality.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <syslog.h>
#include <unistd.h>
#if HAVE_VALGRIND_VALGRIND_H
#include <valgrind/valgrind.h>
#endif
#include "alloc-util.h"
#include "architecture.h"
#include "argv-util.h"
#include "env-file.h"
#include "env-util.h"
#include "errno-util.h"
#include "escape.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hostname-util.h"
#include "locale-util.h"
#include "log.h"
#include "macro.h"
#include "memory-util.h"
#include "missing_sched.h"
#include "missing_syscall.h"
#include "mountpoint-util.h"
#include "namespace-util.h"
#include "nulstr-util.h"
#include "parse-util.h"
#include "path-util.h"
#include "process-util.h"
#include "raw-clone.h"
#include "rlimit-util.h"
#include "signal-util.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-table.h"
#include "string-util.h"
#include "terminal-util.h"
#include "user-util.h"
#include "utf8.h"
/* The kernel limits userspace processes to TASK_COMM_LEN (16 bytes), but allows higher values for its own
* workers, e.g. "kworker/u9:3-kcryptd/253:0". Let's pick a fixed smallish limit that will work for the kernel.
*/
#define COMM_MAX_LEN 128
static int get_process_state(pid_t pid) {
_cleanup_free_ char *line = NULL;
const char *p;
char state;
int r;
assert(pid >= 0);
/* Shortcut: if we are enquired about our own state, we are obviously running */
if (pid == 0 || pid == getpid_cached())
return (unsigned char) 'R';
p = procfs_file_alloca(pid, "stat");
r = read_one_line_file(p, &line);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
p = strrchr(line, ')');
if (!p)
return -EIO;
p++;
if (sscanf(p, " %c", &state) != 1)
return -EIO;
return (unsigned char) state;
}
int get_process_comm(pid_t pid, char **ret) {
_cleanup_free_ char *escaped = NULL, *comm = NULL;
int r;
assert(ret);
assert(pid >= 0);
if (pid == 0 || pid == getpid_cached()) {
comm = new0(char, TASK_COMM_LEN + 1); /* Must fit in 16 byte according to prctl(2) */
if (!comm)
return -ENOMEM;
if (prctl(PR_GET_NAME, comm) < 0)
return -errno;
} else {
const char *p;
p = procfs_file_alloca(pid, "comm");
/* Note that process names of kernel threads can be much longer than TASK_COMM_LEN */
r = read_one_line_file(p, &comm);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
}
escaped = new(char, COMM_MAX_LEN);
if (!escaped)
return -ENOMEM;
/* Escape unprintable characters, just in case, but don't grow the string beyond the underlying size */
cellescape(escaped, COMM_MAX_LEN, comm);
*ret = TAKE_PTR(escaped);
return 0;
}
static int get_process_cmdline_nulstr(
pid_t pid,
size_t max_size,
ProcessCmdlineFlags flags,
char **ret,
size_t *ret_size) {
const char *p;
char *t;
size_t k;
int r;
/* Retrieves a process' command line as a "sized nulstr", i.e. possibly without the last NUL, but
* with a specified size.
*
* If PROCESS_CMDLINE_COMM_FALLBACK is specified in flags and the process has no command line set
* (the case for kernel threads), or has a command line that resolves to the empty string, will
* return the "comm" name of the process instead. This will use at most _SC_ARG_MAX bytes of input
* data.
*
* Returns an error, 0 if output was read but is truncated, 1 otherwise.
*/
p = procfs_file_alloca(pid, "cmdline");
r = read_virtual_file(p, max_size, &t, &k); /* Let's assume that each input byte results in >= 1
* columns of output. We ignore zero-width codepoints. */
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
if (k == 0) {
t = mfree(t);
if (!(flags & PROCESS_CMDLINE_COMM_FALLBACK))
return -ENOENT;
/* Kernel threads have no argv[] */
_cleanup_free_ char *comm = NULL;
r = get_process_comm(pid, &comm);
if (r < 0)
return r;
t = strjoin("[", comm, "]");
if (!t)
return -ENOMEM;
k = strlen(t);
r = k <= max_size;
if (r == 0) /* truncation */
t[max_size] = '\0';
}
*ret = t;
*ret_size = k;
return r;
}
int get_process_cmdline(pid_t pid, size_t max_columns, ProcessCmdlineFlags flags, char **ret) {
_cleanup_free_ char *t = NULL;
size_t k;
char *ans;
assert(pid >= 0);
assert(ret);
/* Retrieve and format a commandline. See above for discussion of retrieval options.
*
* There are two main formatting modes:
*
* - when PROCESS_CMDLINE_QUOTE is specified, output is quoted in C/Python style. If no shell special
* characters are present, this output can be copy-pasted into the terminal to execute. UTF-8
* output is assumed.
*
* - otherwise, a compact non-roundtrippable form is returned. Non-UTF8 bytes are replaced by <20>. The
* returned string is of the specified console width at most, abbreviated with an ellipsis.
*
* Returns -ESRCH if the process doesn't exist, and -ENOENT if the process has no command line (and
* PROCESS_CMDLINE_COMM_FALLBACK is not specified). Returns 0 and sets *line otherwise. */
int full = get_process_cmdline_nulstr(pid, max_columns, flags, &t, &k);
if (full < 0)
return full;
if (flags & (PROCESS_CMDLINE_QUOTE | PROCESS_CMDLINE_QUOTE_POSIX)) {
ShellEscapeFlags shflags = SHELL_ESCAPE_EMPTY |
FLAGS_SET(flags, PROCESS_CMDLINE_QUOTE_POSIX) * SHELL_ESCAPE_POSIX;
assert(!(flags & PROCESS_CMDLINE_USE_LOCALE));
_cleanup_strv_free_ char **args = NULL;
args = strv_parse_nulstr(t, k);
if (!args)
return -ENOMEM;
/* Drop trailing empty strings. See issue #21186. */
STRV_FOREACH_BACKWARDS(p, args) {
if (!isempty(*p))
break;
*p = mfree(*p);
}
ans = quote_command_line(args, shflags);
if (!ans)
return -ENOMEM;
} else {
/* Arguments are separated by NULs. Let's replace those with spaces. */
for (size_t i = 0; i < k - 1; i++)
if (t[i] == '\0')
t[i] = ' ';
delete_trailing_chars(t, WHITESPACE);
bool eight_bit = (flags & PROCESS_CMDLINE_USE_LOCALE) && !is_locale_utf8();
ans = escape_non_printable_full(t, max_columns,
eight_bit * XESCAPE_8_BIT | !full * XESCAPE_FORCE_ELLIPSIS);
if (!ans)
return -ENOMEM;
ans = str_realloc(ans);
}
*ret = ans;
return 0;
}
int container_get_leader(const char *machine, pid_t *pid) {
_cleanup_free_ char *s = NULL, *class = NULL;
const char *p;
pid_t leader;
int r;
assert(machine);
assert(pid);
if (streq(machine, ".host")) {
*pid = 1;
return 0;
}
if (!hostname_is_valid(machine, 0))
return -EINVAL;
p = strjoina("/run/systemd/machines/", machine);
r = parse_env_file(NULL, p,
"LEADER", &s,
"CLASS", &class);
if (r == -ENOENT)
return -EHOSTDOWN;
if (r < 0)
return r;
if (!s)
return -EIO;
if (!streq_ptr(class, "container"))
return -EIO;
r = parse_pid(s, &leader);
if (r < 0)
return r;
if (leader <= 1)
return -EIO;
*pid = leader;
return 0;
}
int is_kernel_thread(pid_t pid) {
_cleanup_free_ char *line = NULL;
unsigned long long flags;
size_t l, i;
const char *p;
char *q;
int r;
if (IN_SET(pid, 0, 1) || pid == getpid_cached()) /* pid 1, and we ourselves certainly aren't a kernel thread */
return 0;
if (!pid_is_valid(pid))
return -EINVAL;
p = procfs_file_alloca(pid, "stat");
r = read_one_line_file(p, &line);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
/* Skip past the comm field */
q = strrchr(line, ')');
if (!q)
return -EINVAL;
q++;
/* Skip 6 fields to reach the flags field */
for (i = 0; i < 6; i++) {
l = strspn(q, WHITESPACE);
if (l < 1)
return -EINVAL;
q += l;
l = strcspn(q, WHITESPACE);
if (l < 1)
return -EINVAL;
q += l;
}
/* Skip preceding whitespace */
l = strspn(q, WHITESPACE);
if (l < 1)
return -EINVAL;
q += l;
/* Truncate the rest */
l = strcspn(q, WHITESPACE);
if (l < 1)
return -EINVAL;
q[l] = 0;
r = safe_atollu(q, &flags);
if (r < 0)
return r;
return !!(flags & PF_KTHREAD);
}
int get_process_capeff(pid_t pid, char **ret) {
const char *p;
int r;
assert(pid >= 0);
assert(ret);
p = procfs_file_alloca(pid, "status");
r = get_proc_field(p, "CapEff", WHITESPACE, ret);
if (r == -ENOENT)
return -ESRCH;
return r;
}
static int get_process_link_contents(pid_t pid, const char *proc_file, char **ret) {
const char *p;
int r;
assert(proc_file);
p = procfs_file_alloca(pid, proc_file);
r = readlink_malloc(p, ret);
return r == -ENOENT ? -ESRCH : r;
}
int get_process_exe(pid_t pid, char **ret) {
char *d;
int r;
assert(pid >= 0);
r = get_process_link_contents(pid, "exe", ret);
if (r < 0)
return r;
if (ret) {
d = endswith(*ret, " (deleted)");
if (d)
*d = '\0';
}
return 0;
}
static int get_process_id(pid_t pid, const char *field, uid_t *ret) {
_cleanup_fclose_ FILE *f = NULL;
const char *p;
int r;
assert(field);
assert(ret);
if (pid < 0)
return -EINVAL;
p = procfs_file_alloca(pid, "status");
r = fopen_unlocked(p, "re", &f);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
for (;;) {
_cleanup_free_ char *line = NULL;
char *l;
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0)
return r;
if (r == 0)
break;
l = strstrip(line);
if (startswith(l, field)) {
l += strlen(field);
l += strspn(l, WHITESPACE);
l[strcspn(l, WHITESPACE)] = 0;
return parse_uid(l, ret);
}
}
return -EIO;
}
int get_process_uid(pid_t pid, uid_t *ret) {
if (pid == 0 || pid == getpid_cached()) {
*ret = getuid();
return 0;
}
return get_process_id(pid, "Uid:", ret);
}
int get_process_gid(pid_t pid, gid_t *ret) {
if (pid == 0 || pid == getpid_cached()) {
*ret = getgid();
return 0;
}
assert_cc(sizeof(uid_t) == sizeof(gid_t));
return get_process_id(pid, "Gid:", ret);
}
int get_process_cwd(pid_t pid, char **ret) {
assert(pid >= 0);
if (pid == 0 || pid == getpid_cached())
return safe_getcwd(ret);
return get_process_link_contents(pid, "cwd", ret);
}
int get_process_root(pid_t pid, char **ret) {
assert(pid >= 0);
return get_process_link_contents(pid, "root", ret);
}
#define ENVIRONMENT_BLOCK_MAX (5U*1024U*1024U)
int get_process_environ(pid_t pid, char **ret) {
_cleanup_fclose_ FILE *f = NULL;
_cleanup_free_ char *outcome = NULL;
size_t sz = 0;
const char *p;
int r;
assert(pid >= 0);
assert(ret);
p = procfs_file_alloca(pid, "environ");
r = fopen_unlocked(p, "re", &f);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
for (;;) {
char c;
if (sz >= ENVIRONMENT_BLOCK_MAX)
return -ENOBUFS;
if (!GREEDY_REALLOC(outcome, sz + 5))
return -ENOMEM;
r = safe_fgetc(f, &c);
if (r < 0)
return r;
if (r == 0)
break;
if (c == '\0')
outcome[sz++] = '\n';
else
sz += cescape_char(c, outcome + sz);
}
outcome[sz] = '\0';
*ret = TAKE_PTR(outcome);
return 0;
}
int get_process_ppid(pid_t pid, pid_t *ret) {
_cleanup_free_ char *line = NULL;
unsigned long ppid;
const char *p;
int r;
assert(pid >= 0);
if (pid == 0 || pid == getpid_cached()) {
if (ret)
*ret = getppid();
return 0;
}
if (pid == 1) /* PID 1 has no parent, shortcut this case */
return -EADDRNOTAVAIL;
p = procfs_file_alloca(pid, "stat");
r = read_one_line_file(p, &line);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
/* Let's skip the pid and comm fields. The latter is enclosed in () but does not escape any () in its
* value, so let's skip over it manually */
p = strrchr(line, ')');
if (!p)
return -EIO;
p++;
if (sscanf(p, " "
"%*c " /* state */
"%lu ", /* ppid */
&ppid) != 1)
return -EIO;
/* If ppid is zero the process has no parent. Which might be the case for PID 1 but also for
* processes originating in other namespaces that are inserted into a pidns. Return a recognizable
* error in this case. */
if (ppid == 0)
return -EADDRNOTAVAIL;
if ((pid_t) ppid < 0 || (unsigned long) (pid_t) ppid != ppid)
return -ERANGE;
if (ret)
*ret = (pid_t) ppid;
return 0;
}
int get_process_umask(pid_t pid, mode_t *ret) {
_cleanup_free_ char *m = NULL;
const char *p;
int r;
assert(pid >= 0);
assert(ret);
p = procfs_file_alloca(pid, "status");
r = get_proc_field(p, "Umask", WHITESPACE, &m);
if (r == -ENOENT)
return -ESRCH;
return parse_mode(m, ret);
}
int wait_for_terminate(pid_t pid, siginfo_t *status) {
siginfo_t dummy;
assert(pid >= 1);
if (!status)
status = &dummy;
for (;;) {
zero(*status);
if (waitid(P_PID, pid, status, WEXITED) < 0) {
if (errno == EINTR)
continue;
return negative_errno();
}
return 0;
}
}
/*
* Return values:
* < 0 : wait_for_terminate() failed to get the state of the
* process, the process was terminated by a signal, or
* failed for an unknown reason.
* >=0 : The process terminated normally, and its exit code is
* returned.
*
* That is, success is indicated by a return value of zero, and an
* error is indicated by a non-zero value.
*
* A warning is emitted if the process terminates abnormally,
* and also if it returns non-zero unless check_exit_code is true.
*/
int wait_for_terminate_and_check(const char *name, pid_t pid, WaitFlags flags) {
_cleanup_free_ char *buffer = NULL;
siginfo_t status;
int r, prio;
assert(pid > 1);
if (!name) {
r = get_process_comm(pid, &buffer);
if (r < 0)
log_debug_errno(r, "Failed to acquire process name of " PID_FMT ", ignoring: %m", pid);
else
name = buffer;
}
prio = flags & WAIT_LOG_ABNORMAL ? LOG_ERR : LOG_DEBUG;
r = wait_for_terminate(pid, &status);
if (r < 0)
return log_full_errno(prio, r, "Failed to wait for %s: %m", strna(name));
if (status.si_code == CLD_EXITED) {
if (status.si_status != EXIT_SUCCESS)
log_full(flags & WAIT_LOG_NON_ZERO_EXIT_STATUS ? LOG_ERR : LOG_DEBUG,
"%s failed with exit status %i.", strna(name), status.si_status);
else
log_debug("%s succeeded.", name);
return status.si_status;
} else if (IN_SET(status.si_code, CLD_KILLED, CLD_DUMPED)) {
log_full(prio, "%s terminated by signal %s.", strna(name), signal_to_string(status.si_status));
return -EPROTO;
}
log_full(prio, "%s failed due to unknown reason.", strna(name));
return -EPROTO;
}
/*
* Return values:
*
* < 0 : wait_for_terminate_with_timeout() failed to get the state of the process, the process timed out, the process
* was terminated by a signal, or failed for an unknown reason.
*
* >=0 : The process terminated normally with no failures.
*
* Success is indicated by a return value of zero, a timeout is indicated by ETIMEDOUT, and all other child failure
* states are indicated by error is indicated by a non-zero value.
*
* This call assumes SIGCHLD has been blocked already, in particular before the child to wait for has been forked off
* to remain entirely race-free.
*/
int wait_for_terminate_with_timeout(pid_t pid, usec_t timeout) {
sigset_t mask;
int r;
usec_t until;
assert_se(sigemptyset(&mask) == 0);
assert_se(sigaddset(&mask, SIGCHLD) == 0);
/* Drop into a sigtimewait-based timeout. Waiting for the
* pid to exit. */
until = usec_add(now(CLOCK_MONOTONIC), timeout);
for (;;) {
usec_t n;
siginfo_t status = {};
n = now(CLOCK_MONOTONIC);
if (n >= until)
break;
r = RET_NERRNO(sigtimedwait(&mask, NULL, TIMESPEC_STORE(until - n)));
/* Assuming we woke due to the child exiting. */
if (waitid(P_PID, pid, &status, WEXITED|WNOHANG) == 0) {
if (status.si_pid == pid) {
/* This is the correct child. */
if (status.si_code == CLD_EXITED)
return status.si_status == 0 ? 0 : -EPROTO;
else
return -EPROTO;
}
}
/* Not the child, check for errors and proceed appropriately */
if (r < 0) {
switch (r) {
case -EAGAIN:
/* Timed out, child is likely hung. */
return -ETIMEDOUT;
case -EINTR:
/* Received a different signal and should retry */
continue;
default:
/* Return any unexpected errors */
return r;
}
}
}
return -EPROTO;
}
void sigkill_wait(pid_t pid) {
assert(pid > 1);
(void) kill(pid, SIGKILL);
(void) wait_for_terminate(pid, NULL);
}
void sigkill_waitp(pid_t *pid) {
PROTECT_ERRNO;
if (!pid)
return;
if (*pid <= 1)
return;
sigkill_wait(*pid);
}
void sigterm_wait(pid_t pid) {
assert(pid > 1);
(void) kill_and_sigcont(pid, SIGTERM);
(void) wait_for_terminate(pid, NULL);
}
void sigkill_nowait(pid_t pid) {
assert(pid > 1);
(void) kill(pid, SIGKILL);
}
void sigkill_nowaitp(pid_t *pid) {
PROTECT_ERRNO;
if (!pid)
return;
if (*pid <= 1)
return;
sigkill_nowait(*pid);
}
int kill_and_sigcont(pid_t pid, int sig) {
int r;
r = RET_NERRNO(kill(pid, sig));
/* If this worked, also send SIGCONT, unless we already just sent a SIGCONT, or SIGKILL was sent which isn't
* affected by a process being suspended anyway. */
if (r >= 0 && !IN_SET(sig, SIGCONT, SIGKILL))
(void) kill(pid, SIGCONT);
return r;
}
int getenv_for_pid(pid_t pid, const char *field, char **ret) {
_cleanup_fclose_ FILE *f = NULL;
char *value = NULL;
const char *path;
size_t l, sum = 0;
int r;
assert(pid >= 0);
assert(field);
assert(ret);
if (pid == 0 || pid == getpid_cached()) {
const char *e;
e = getenv(field);
if (!e) {
*ret = NULL;
return 0;
}
value = strdup(e);
if (!value)
return -ENOMEM;
*ret = value;
return 1;
}
if (!pid_is_valid(pid))
return -EINVAL;
path = procfs_file_alloca(pid, "environ");
r = fopen_unlocked(path, "re", &f);
if (r == -ENOENT)
return -ESRCH;
if (r < 0)
return r;
l = strlen(field);
for (;;) {
_cleanup_free_ char *line = NULL;
if (sum > ENVIRONMENT_BLOCK_MAX) /* Give up searching eventually */
return -ENOBUFS;
r = read_nul_string(f, LONG_LINE_MAX, &line);
if (r < 0)
return r;
if (r == 0) /* EOF */
break;
sum += r;
if (strneq(line, field, l) && line[l] == '=') {
value = strdup(line + l + 1);
if (!value)
return -ENOMEM;
*ret = value;
return 1;
}
}
*ret = NULL;
return 0;
}
int pid_is_my_child(pid_t pid) {
pid_t ppid;
int r;
if (pid <= 1)
return false;
r = get_process_ppid(pid, &ppid);
if (r < 0)
return r;
return ppid == getpid_cached();
}
bool pid_is_unwaited(pid_t pid) {
/* Checks whether a PID is still valid at all, including a zombie */
if (pid < 0)
return false;
if (pid <= 1) /* If we or PID 1 would be dead and have been waited for, this code would not be running */
return true;
if (pid == getpid_cached())
return true;
if (kill(pid, 0) >= 0)
return true;
return errno != ESRCH;
}
bool pid_is_alive(pid_t pid) {
int r;
/* Checks whether a PID is still valid and not a zombie */
if (pid < 0)
return false;
if (pid <= 1) /* If we or PID 1 would be a zombie, this code would not be running */
return true;
if (pid == getpid_cached())
return true;
r = get_process_state(pid);
if (IN_SET(r, -ESRCH, 'Z'))
return false;
return true;
}
int pid_from_same_root_fs(pid_t pid) {
const char *root;
if (pid < 0)
return false;
if (pid == 0 || pid == getpid_cached())
return true;
root = procfs_file_alloca(pid, "root");
return files_same(root, "/proc/1/root", 0);
}
bool is_main_thread(void) {
static thread_local int cached = 0;
if (_unlikely_(cached == 0))
cached = getpid_cached() == gettid() ? 1 : -1;
return cached > 0;
}
bool oom_score_adjust_is_valid(int oa) {
return oa >= OOM_SCORE_ADJ_MIN && oa <= OOM_SCORE_ADJ_MAX;
}
unsigned long personality_from_string(const char *p) {
Architecture architecture;
if (!p)
return PERSONALITY_INVALID;
/* Parse a personality specifier. We use our own identifiers that indicate specific ABIs, rather than just
* hints regarding the register size, since we want to keep things open for multiple locally supported ABIs for
* the same register size. */
architecture = architecture_from_string(p);
if (architecture < 0)
return PERSONALITY_INVALID;
if (architecture == native_architecture())
return PER_LINUX;
#ifdef ARCHITECTURE_SECONDARY
if (architecture == ARCHITECTURE_SECONDARY)
return PER_LINUX32;
#endif
return PERSONALITY_INVALID;
}
const char* personality_to_string(unsigned long p) {
Architecture architecture = _ARCHITECTURE_INVALID;
if (p == PER_LINUX)
architecture = native_architecture();
#ifdef ARCHITECTURE_SECONDARY
else if (p == PER_LINUX32)
architecture = ARCHITECTURE_SECONDARY;
#endif
if (architecture < 0)
return NULL;
return architecture_to_string(architecture);
}
int safe_personality(unsigned long p) {
int ret;
/* So here's the deal, personality() is weirdly defined by glibc. In some cases it returns a failure via errno,
* and in others as negative return value containing an errno-like value. Let's work around this: this is a
* wrapper that uses errno if it is set, and uses the return value otherwise. And then it sets both errno and
* the return value indicating the same issue, so that we are definitely on the safe side.
*
* See https://github.com/systemd/systemd/issues/6737 */
errno = 0;
ret = personality(p);
if (ret < 0) {
if (errno != 0)
return -errno;
errno = -ret;
}
return ret;
}
int opinionated_personality(unsigned long *ret) {
int current;
/* Returns the current personality, or PERSONALITY_INVALID if we can't determine it. This function is a bit
* opinionated though, and ignores all the finer-grained bits and exotic personalities, only distinguishing the
* two most relevant personalities: PER_LINUX and PER_LINUX32. */
current = safe_personality(PERSONALITY_INVALID);
if (current < 0)
return current;
if (((unsigned long) current & 0xffff) == PER_LINUX32)
*ret = PER_LINUX32;
else
*ret = PER_LINUX;
return 0;
}
void valgrind_summary_hack(void) {
#if HAVE_VALGRIND_VALGRIND_H
if (getpid_cached() == 1 && RUNNING_ON_VALGRIND) {
pid_t pid;
pid = raw_clone(SIGCHLD);
if (pid < 0)
log_emergency_errno(errno, "Failed to fork off valgrind helper: %m");
else if (pid == 0)
exit(EXIT_SUCCESS);
else {
log_info("Spawned valgrind helper as PID "PID_FMT".", pid);
(void) wait_for_terminate(pid, NULL);
}
}
#endif
}
int pid_compare_func(const pid_t *a, const pid_t *b) {
/* Suitable for usage in qsort() */
return CMP(*a, *b);
}
/* The cached PID, possible values:
*
* == UNSET [0] → cache not initialized yet
* == BUSY [-1] → some thread is initializing it at the moment
* any other → the cached PID
*/
#define CACHED_PID_UNSET ((pid_t) 0)
#define CACHED_PID_BUSY ((pid_t) -1)
static pid_t cached_pid = CACHED_PID_UNSET;
void reset_cached_pid(void) {
/* Invoked in the child after a fork(), i.e. at the first moment the PID changed */
cached_pid = CACHED_PID_UNSET;
}
pid_t getpid_cached(void) {
static bool installed = false;
pid_t current_value = CACHED_PID_UNSET;
/* getpid_cached() is much like getpid(), but caches the value in local memory, to avoid having to invoke a
* system call each time. This restores glibc behaviour from before 2.24, when getpid() was unconditionally
* cached. Starting with 2.24 getpid() started to become prohibitively expensive when used for detecting when
* objects were used across fork()s. With this caching the old behaviour is somewhat restored.
*
* https://bugzilla.redhat.com/show_bug.cgi?id=1443976
* https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c579f48edba88380635ab98cb612030e3ed8691e
*/
__atomic_compare_exchange_n(
&cached_pid,
&current_value,
CACHED_PID_BUSY,
false,
__ATOMIC_SEQ_CST,
__ATOMIC_SEQ_CST);
switch (current_value) {
case CACHED_PID_UNSET: { /* Not initialized yet, then do so now */
pid_t new_pid;
new_pid = raw_getpid();
if (!installed) {
/* __register_atfork() either returns 0 or -ENOMEM, in its glibc implementation. Since it's
* only half-documented (glibc doesn't document it but LSB does — though only superficially)
* we'll check for errors only in the most generic fashion possible. */
if (pthread_atfork(NULL, NULL, reset_cached_pid) != 0) {
/* OOM? Let's try again later */
cached_pid = CACHED_PID_UNSET;
return new_pid;
}
installed = true;
}
cached_pid = new_pid;
return new_pid;
}
case CACHED_PID_BUSY: /* Somebody else is currently initializing */
return raw_getpid();
default: /* Properly initialized */
return current_value;
}
}
int must_be_root(void) {
if (geteuid() == 0)
return 0;
return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Need to be root.");
}
static void restore_sigsetp(sigset_t **ssp) {
if (*ssp)
(void) sigprocmask(SIG_SETMASK, *ssp, NULL);
}
int safe_fork_full(
const char *name,
const int except_fds[],
size_t n_except_fds,
ForkFlags flags,
pid_t *ret_pid) {
pid_t original_pid, pid;
sigset_t saved_ss, ss;
_unused_ _cleanup_(restore_sigsetp) sigset_t *saved_ssp = NULL;
bool block_signals = false, block_all = false;
int prio, r;
/* A wrapper around fork(), that does a couple of important initializations in addition to mere forking. Always
* returns the child's PID in *ret_pid. Returns == 0 in the child, and > 0 in the parent. */
prio = flags & FORK_LOG ? LOG_ERR : LOG_DEBUG;
original_pid = getpid_cached();
if (flags & FORK_FLUSH_STDIO) {
fflush(stdout);
fflush(stderr); /* This one shouldn't be necessary, stderr should be unbuffered anyway, but let's better be safe than sorry */
}
if (flags & (FORK_RESET_SIGNALS|FORK_DEATHSIG)) {
/* We temporarily block all signals, so that the new child has them blocked initially. This way, we can
* be sure that SIGTERMs are not lost we might send to the child. */
assert_se(sigfillset(&ss) >= 0);
block_signals = block_all = true;
} else if (flags & FORK_WAIT) {
/* Let's block SIGCHLD at least, so that we can safely watch for the child process */
assert_se(sigemptyset(&ss) >= 0);
assert_se(sigaddset(&ss, SIGCHLD) >= 0);
block_signals = true;
}
if (block_signals) {
if (sigprocmask(SIG_SETMASK, &ss, &saved_ss) < 0)
return log_full_errno(prio, errno, "Failed to set signal mask: %m");
saved_ssp = &saved_ss;
}
if ((flags & (FORK_NEW_MOUNTNS|FORK_NEW_USERNS)) != 0)
pid = raw_clone(SIGCHLD|
(FLAGS_SET(flags, FORK_NEW_MOUNTNS) ? CLONE_NEWNS : 0) |
(FLAGS_SET(flags, FORK_NEW_USERNS) ? CLONE_NEWUSER : 0));
else
pid = fork();
if (pid < 0)
return log_full_errno(prio, errno, "Failed to fork: %m");
if (pid > 0) {
/* We are in the parent process */
log_debug("Successfully forked off '%s' as PID " PID_FMT ".", strna(name), pid);
if (flags & FORK_WAIT) {
if (block_all) {
/* undo everything except SIGCHLD */
ss = saved_ss;
assert_se(sigaddset(&ss, SIGCHLD) >= 0);
(void) sigprocmask(SIG_SETMASK, &ss, NULL);
}
r = wait_for_terminate_and_check(name, pid, (flags & FORK_LOG ? WAIT_LOG : 0));
if (r < 0)
return r;
if (r != EXIT_SUCCESS) /* exit status > 0 should be treated as failure, too */
return -EPROTO;
}
if (ret_pid)
*ret_pid = pid;
return 1;
}
/* We are in the child process */
/* Restore signal mask manually */
saved_ssp = NULL;
if (flags & FORK_REOPEN_LOG) {
/* Close the logs if requested, before we log anything. And make sure we reopen it if needed. */
log_close();
log_set_open_when_needed(true);
}
if (name) {
r = rename_process(name);
if (r < 0)
log_full_errno(flags & FORK_LOG ? LOG_WARNING : LOG_DEBUG,
r, "Failed to rename process, ignoring: %m");
}
if (flags & (FORK_DEATHSIG|FORK_DEATHSIG_SIGINT))
if (prctl(PR_SET_PDEATHSIG, (flags & FORK_DEATHSIG_SIGINT) ? SIGINT : SIGTERM) < 0) {
log_full_errno(prio, errno, "Failed to set death signal: %m");
_exit(EXIT_FAILURE);
}
if (flags & FORK_RESET_SIGNALS) {
r = reset_all_signal_handlers();
if (r < 0) {
log_full_errno(prio, r, "Failed to reset signal handlers: %m");
_exit(EXIT_FAILURE);
}
/* This implicitly undoes the signal mask stuff we did before the fork()ing above */
r = reset_signal_mask();
if (r < 0) {
log_full_errno(prio, r, "Failed to reset signal mask: %m");
_exit(EXIT_FAILURE);
}
} else if (block_signals) { /* undo what we did above */
if (sigprocmask(SIG_SETMASK, &saved_ss, NULL) < 0) {
log_full_errno(prio, errno, "Failed to restore signal mask: %m");
_exit(EXIT_FAILURE);
}
}
if (flags & FORK_DEATHSIG) {
pid_t ppid;
/* Let's see if the parent PID is still the one we started from? If not, then the parent
* already died by the time we set PR_SET_PDEATHSIG, hence let's emulate the effect */
ppid = getppid();
if (ppid == 0)
/* Parent is in a different PID namespace. */;
else if (ppid != original_pid) {
log_debug("Parent died early, raising SIGTERM.");
(void) raise(SIGTERM);
_exit(EXIT_FAILURE);
}
}
if (FLAGS_SET(flags, FORK_NEW_MOUNTNS | FORK_MOUNTNS_SLAVE)) {
/* Optionally, make sure we never propagate mounts to the host. */
if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0) {
log_full_errno(prio, errno, "Failed to remount root directory as MS_SLAVE: %m");
_exit(EXIT_FAILURE);
}
}
if (FLAGS_SET(flags, FORK_PRIVATE_TMP)) {
assert(FLAGS_SET(flags, FORK_NEW_MOUNTNS));
/* Optionally, overmount new tmpfs instance on /tmp/. */
r = mount_nofollow("tmpfs", "/tmp", "tmpfs",
MS_NOSUID|MS_NODEV,
"mode=01777" TMPFS_LIMITS_RUN);
if (r < 0) {
log_full_errno(prio, r, "Failed to overmount /tmp/: %m");
_exit(EXIT_FAILURE);
}
}
if (flags & FORK_CLOSE_ALL_FDS) {
/* Close the logs here in case it got reopened above, as close_all_fds() would close them for us */
log_close();
r = close_all_fds(except_fds, n_except_fds);
if (r < 0) {
log_full_errno(prio, r, "Failed to close all file descriptors: %m");
_exit(EXIT_FAILURE);
}
}
if (flags & FORK_CLOEXEC_OFF) {
r = fd_cloexec_many(except_fds, n_except_fds, false);
if (r < 0) {
log_full_errno(prio, r, "Failed to turn off O_CLOEXEC on file descriptors: %m");
_exit(EXIT_FAILURE);
}
}
/* When we were asked to reopen the logs, do so again now */
if (flags & FORK_REOPEN_LOG) {
log_open();
log_set_open_when_needed(false);
}
if (flags & FORK_NULL_STDIO) {
r = make_null_stdio();
if (r < 0) {
log_full_errno(prio, r, "Failed to connect stdin/stdout to /dev/null: %m");
_exit(EXIT_FAILURE);
}
} else if (flags & FORK_STDOUT_TO_STDERR) {
if (dup2(STDERR_FILENO, STDOUT_FILENO) < 0) {
log_full_errno(prio, errno, "Failed to connect stdout to stderr: %m");
_exit(EXIT_FAILURE);
}
}
if (flags & FORK_RLIMIT_NOFILE_SAFE) {
r = rlimit_nofile_safe();
if (r < 0) {
log_full_errno(prio, r, "Failed to lower RLIMIT_NOFILE's soft limit to 1K: %m");
_exit(EXIT_FAILURE);
}
}
if (ret_pid)
*ret_pid = getpid_cached();
return 0;
}
int namespace_fork(
const char *outer_name,
const char *inner_name,
const int except_fds[],
size_t n_except_fds,
ForkFlags flags,
int pidns_fd,
int mntns_fd,
int netns_fd,
int userns_fd,
int root_fd,
pid_t *ret_pid) {
int r;
/* This is much like safe_fork(), but forks twice, and joins the specified namespaces in the middle
* process. This ensures that we are fully a member of the destination namespace, with pidns an all, so that
* /proc/self/fd works correctly. */
r = safe_fork_full(outer_name, except_fds, n_except_fds, (flags|FORK_DEATHSIG) & ~(FORK_REOPEN_LOG|FORK_NEW_MOUNTNS|FORK_MOUNTNS_SLAVE), ret_pid);
if (r < 0)
return r;
if (r == 0) {
pid_t pid;
/* Child */
r = namespace_enter(pidns_fd, mntns_fd, netns_fd, userns_fd, root_fd);
if (r < 0) {
log_full_errno(FLAGS_SET(flags, FORK_LOG) ? LOG_ERR : LOG_DEBUG, r, "Failed to join namespace: %m");
_exit(EXIT_FAILURE);
}
/* We mask a few flags here that either make no sense for the grandchild, or that we don't have to do again */
r = safe_fork_full(inner_name, except_fds, n_except_fds, flags & ~(FORK_WAIT|FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_NULL_STDIO), &pid);
if (r < 0)
_exit(EXIT_FAILURE);
if (r == 0) {
/* Child */
if (ret_pid)
*ret_pid = pid;
return 0;
}
r = wait_for_terminate_and_check(inner_name, pid, FLAGS_SET(flags, FORK_LOG) ? WAIT_LOG : 0);
if (r < 0)
_exit(EXIT_FAILURE);
_exit(r);
}
return 1;
}
int set_oom_score_adjust(int value) {
char t[DECIMAL_STR_MAX(int)];
xsprintf(t, "%i", value);
return write_string_file("/proc/self/oom_score_adj", t,
WRITE_STRING_FILE_VERIFY_ON_FAILURE|WRITE_STRING_FILE_DISABLE_BUFFER);
}
int get_oom_score_adjust(int *ret) {
_cleanup_free_ char *t = NULL;
int r, a;
r = read_virtual_file("/proc/self/oom_score_adj", SIZE_MAX, &t, NULL);
if (r < 0)
return r;
delete_trailing_chars(t, WHITESPACE);
assert_se(safe_atoi(t, &a) >= 0);
assert_se(oom_score_adjust_is_valid(a));
if (ret)
*ret = a;
return 0;
}
int pidfd_get_pid(int fd, pid_t *ret) {
char path[STRLEN("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
_cleanup_free_ char *fdinfo = NULL;
char *p;
int r;
if (fd < 0)
return -EBADF;
xsprintf(path, "/proc/self/fdinfo/%i", fd);
r = read_full_virtual_file(path, &fdinfo, NULL);
if (r == -ENOENT) /* if fdinfo doesn't exist we assume the process does not exist */
return -ESRCH;
if (r < 0)
return r;
p = startswith(fdinfo, "Pid:");
if (!p) {
p = strstr(fdinfo, "\nPid:");
if (!p)
return -ENOTTY; /* not a pidfd? */
p += 5;
}
p += strspn(p, WHITESPACE);
p[strcspn(p, WHITESPACE)] = 0;
return parse_pid(p, ret);
}
int pidfd_verify_pid(int pidfd, pid_t pid) {
pid_t current_pid;
int r;
assert(pidfd >= 0);
assert(pid > 0);
r = pidfd_get_pid(pidfd, &current_pid);
if (r < 0)
return r;
return current_pid != pid ? -ESRCH : 0;
}
static int rlimit_to_nice(rlim_t limit) {
if (limit <= 1)
return PRIO_MAX-1; /* i.e. 19 */
if (limit >= -PRIO_MIN + PRIO_MAX)
return PRIO_MIN; /* i.e. -20 */
return PRIO_MAX - (int) limit;
}
int setpriority_closest(int priority) {
int current, limit, saved_errno;
struct rlimit highest;
/* Try to set requested nice level */
if (setpriority(PRIO_PROCESS, 0, priority) >= 0)
return 1;
/* Permission failed */
saved_errno = -errno;
if (!ERRNO_IS_PRIVILEGE(saved_errno))
return saved_errno;
errno = 0;
current = getpriority(PRIO_PROCESS, 0);
if (errno != 0)
return -errno;
if (priority == current)
return 1;
/* Hmm, we'd expect that raising the nice level from our status quo would always work. If it doesn't,
* then the whole setpriority() system call is blocked to us, hence let's propagate the error
* right-away */
if (priority > current)
return saved_errno;
if (getrlimit(RLIMIT_NICE, &highest) < 0)
return -errno;
limit = rlimit_to_nice(highest.rlim_cur);
/* We are already less nice than limit allows us */
if (current < limit) {
log_debug("Cannot raise nice level, permissions and the resource limit do not allow it.");
return 0;
}
/* Push to the allowed limit */
if (setpriority(PRIO_PROCESS, 0, limit) < 0)
return -errno;
log_debug("Cannot set requested nice level (%i), used next best (%i).", priority, limit);
return 0;
}
_noreturn_ void freeze(void) {
log_close();
/* Make sure nobody waits for us (i.e. on one of our sockets) anymore. Note that we use
* close_all_fds_without_malloc() instead of plain close_all_fds() here, since we want this function
* to be compatible with being called from signal handlers. */
(void) close_all_fds_without_malloc(NULL, 0);
/* Let's not freeze right away, but keep reaping zombies. */
for (;;) {
siginfo_t si = {};
if (waitid(P_ALL, 0, &si, WEXITED) < 0 && errno != EINTR)
break;
}
/* waitid() failed with an unexpected error, things are really borked. Freeze now! */
for (;;)
pause();
}
static const char *const sigchld_code_table[] = {
[CLD_EXITED] = "exited",
[CLD_KILLED] = "killed",
[CLD_DUMPED] = "dumped",
[CLD_TRAPPED] = "trapped",
[CLD_STOPPED] = "stopped",
[CLD_CONTINUED] = "continued",
};
DEFINE_STRING_TABLE_LOOKUP(sigchld_code, int);
static const char* const sched_policy_table[] = {
[SCHED_OTHER] = "other",
[SCHED_BATCH] = "batch",
[SCHED_IDLE] = "idle",
[SCHED_FIFO] = "fifo",
[SCHED_RR] = "rr",
};
DEFINE_STRING_TABLE_LOOKUP_WITH_FALLBACK(sched_policy, int, INT_MAX);
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