termux-packages/packages/libandroid-spawn/posix_spawn.cpp

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/*
* Copyright (C) 2017 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <android/fdsan.h>
#include "posix_spawn.h"
// Bionic "private/ScopedSignalBlocker.h" + one macro needed
#define BIONIC_DISALLOW_COPY_AND_ASSIGN(TypeName) \
TypeName(const TypeName&) = delete; \
void operator=(const TypeName&) = delete
class ScopedSignalBlocker {
public:
// Block all signals.
explicit ScopedSignalBlocker() {
sigset_t set;
sigfillset(&set);
sigprocmask(SIG_BLOCK, &set, &old_set_);
}
// Block just the specified signal.
explicit ScopedSignalBlocker(int signal) {
sigset_t set = {};
sigaddset(&set, signal);
sigprocmask(SIG_BLOCK, &set, &old_set_);
}
~ScopedSignalBlocker() {
reset();
}
void reset() {
sigprocmask(SIG_SETMASK, &old_set_, nullptr);
}
sigset_t old_set_;
BIONIC_DISALLOW_COPY_AND_ASSIGN(ScopedSignalBlocker);
};
// Bionic "private/SigSetConverter.h"
union SigSetConverter {
int bsd;
sigset_t sigset;
sigset64_t sigset64;
};
enum Action {
kOpen,
kClose,
kDup2
};
struct __posix_spawn_file_action {
__posix_spawn_file_action* next;
Action what;
int fd;
int new_fd;
char* path;
int flags;
mode_t mode;
void Do() {
if (what == kOpen) {
fd = open(path, flags, mode);
if (fd == -1) _exit(127);
// If it didn't land where we wanted it, move it.
if (fd != new_fd) {
if (dup2(fd, new_fd) == -1) _exit(127);
close(fd);
}
} else if (what == kClose) {
// Failure to close is ignored.
close(fd);
} else {
if (dup2(fd, new_fd) == -1) _exit(127);
}
}
};
struct __posix_spawn_file_actions {
__posix_spawn_file_action* head;
__posix_spawn_file_action* last;
void Do() {
for (__posix_spawn_file_action* action = head; action != nullptr; action = action->next) {
action->Do();
}
}
};
struct __posix_spawnattr {
short flags;
pid_t pgroup;
sched_param schedparam;
int schedpolicy;
SigSetConverter sigmask;
SigSetConverter sigdefault;
};
static void ApplyAttrs(short flags, const posix_spawnattr_t* attr) {
// POSIX: "If POSIX_SPAWN_SETSIGDEF is set ... signals in sigdefault ...
// shall be set to their default actions in the child process."
// POSIX: "Signals set to be caught by the calling process shall be
// set to the default action in the child process."
bool use_sigdefault = ((flags & POSIX_SPAWN_SETSIGDEF) != 0);
const struct sigaction default_sa = { .sa_handler = SIG_DFL };
for (int s = 1; s < _NSIG; ++s) {
bool reset = false;
if (use_sigdefault && sigismember(&(*attr)->sigdefault.sigset, s)) {
reset = true;
} else {
struct sigaction current;
if (sigaction(s, nullptr, &current) == -1) _exit(127);
reset = (current.sa_handler != SIG_IGN && current.sa_handler != SIG_DFL);
}
if (reset && sigaction(s, &default_sa, nullptr) == -1) _exit(127);
}
if ((flags & POSIX_SPAWN_SETPGROUP) != 0 && setpgid(0, (*attr)->pgroup) == -1) _exit(127);
if ((flags & POSIX_SPAWN_SETSID) != 0 && setsid() == -1) _exit(127);
// POSIX_SPAWN_SETSCHEDULER overrides POSIX_SPAWN_SETSCHEDPARAM, but it is not an error
// to set both.
if ((flags & POSIX_SPAWN_SETSCHEDULER) != 0) {
if (sched_setscheduler(0, (*attr)->schedpolicy, &(*attr)->schedparam) == -1) _exit(127);
} else if ((flags & POSIX_SPAWN_SETSCHEDPARAM) != 0) {
if (sched_setparam(0, &(*attr)->schedparam) == -1) _exit(127);
}
if ((flags & POSIX_SPAWN_RESETIDS) != 0) {
if (seteuid(getuid()) == -1 || setegid(getgid()) == -1) _exit(127);
}
if ((flags & POSIX_SPAWN_SETSIGMASK) != 0) {
if (sigprocmask(SIG_SETMASK, &(*attr)->sigmask.sigset, nullptr)) _exit(127);
}
}
static int posix_spawn(pid_t* pid_ptr,
const char* path,
const posix_spawn_file_actions_t* actions,
const posix_spawnattr_t* attr,
char* const argv[],
char* const env[],
int exec_fn(const char* path, char* const argv[], char* const env[])) {
// See http://man7.org/linux/man-pages/man3/posix_spawn.3.html
// and http://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_spawn.html
ScopedSignalBlocker ssb;
short flags = attr ? (*attr)->flags : 0;
bool use_vfork = ((flags & POSIX_SPAWN_USEVFORK) != 0) || (actions == nullptr && flags == 0);
pid_t pid = use_vfork ? vfork() : fork();
if (pid == -1) return errno;
if (pid == 0) {
// Child.
ApplyAttrs(flags, attr);
if (actions) (*actions)->Do();
if ((flags & POSIX_SPAWN_SETSIGMASK) == 0) ssb.reset();
exec_fn(path, argv, env ? env : environ);
_exit(127);
}
// Parent.
if (pid_ptr) *pid_ptr = pid;
return 0;
}
int posix_spawn(pid_t* pid, const char* path, const posix_spawn_file_actions_t* actions,
const posix_spawnattr_t* attr, char* const argv[], char* const env[]) {
return posix_spawn(pid, path, actions, attr, argv, env, execve);
}
int posix_spawnp(pid_t* pid, const char* file, const posix_spawn_file_actions_t* actions,
const posix_spawnattr_t* attr, char* const argv[], char* const env[]) {
return posix_spawn(pid, file, actions, attr, argv, env, execvpe);
}
int posix_spawnattr_init(posix_spawnattr_t* attr) {
*attr = reinterpret_cast<__posix_spawnattr*>(calloc(1, sizeof(__posix_spawnattr)));
return (*attr == nullptr) ? errno : 0;
}
int posix_spawnattr_destroy(posix_spawnattr_t* attr) {
free(*attr);
*attr = nullptr;
return 0;
}
int posix_spawnattr_setflags(posix_spawnattr_t* attr, short flags) {
if ((flags & ~(POSIX_SPAWN_RESETIDS | POSIX_SPAWN_SETPGROUP | POSIX_SPAWN_SETSIGDEF |
POSIX_SPAWN_SETSIGMASK | POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER |
POSIX_SPAWN_USEVFORK | POSIX_SPAWN_SETSID)) != 0) {
return EINVAL;
}
(*attr)->flags = flags;
return 0;
}
int posix_spawnattr_getflags(const posix_spawnattr_t* attr, short* flags) {
*flags = (*attr)->flags;
return 0;
}
int posix_spawnattr_setpgroup(posix_spawnattr_t* attr, pid_t pgroup) {
(*attr)->pgroup = pgroup;
return 0;
}
int posix_spawnattr_getpgroup(const posix_spawnattr_t* attr, pid_t* pgroup) {
*pgroup = (*attr)->pgroup;
return 0;
}
int posix_spawnattr_setsigmask(posix_spawnattr_t* attr, const sigset_t* mask) {
(*attr)->sigmask.sigset = *mask;
return 0;
}
int posix_spawnattr_setsigmask64(posix_spawnattr_t* attr, const sigset64_t* mask) {
(*attr)->sigmask.sigset64 = *mask;
return 0;
}
int posix_spawnattr_getsigmask(const posix_spawnattr_t* attr, sigset_t* mask) {
*mask = (*attr)->sigmask.sigset;
return 0;
}
int posix_spawnattr_getsigmask64(const posix_spawnattr_t* attr, sigset64_t* mask) {
*mask = (*attr)->sigmask.sigset64;
return 0;
}
int posix_spawnattr_setsigdefault(posix_spawnattr_t* attr, const sigset_t* mask) {
(*attr)->sigdefault.sigset = *mask;
return 0;
}
int posix_spawnattr_setsigdefault64(posix_spawnattr_t* attr, const sigset64_t* mask) {
(*attr)->sigdefault.sigset64 = *mask;
return 0;
}
int posix_spawnattr_getsigdefault(const posix_spawnattr_t* attr, sigset_t* mask) {
*mask = (*attr)->sigdefault.sigset;
return 0;
}
int posix_spawnattr_getsigdefault64(const posix_spawnattr_t* attr, sigset64_t* mask) {
*mask = (*attr)->sigdefault.sigset64;
return 0;
}
int posix_spawnattr_setschedparam(posix_spawnattr_t* attr, const struct sched_param* param) {
(*attr)->schedparam = *param;
return 0;
}
int posix_spawnattr_getschedparam(const posix_spawnattr_t* attr, struct sched_param* param) {
*param = (*attr)->schedparam;
return 0;
}
int posix_spawnattr_setschedpolicy(posix_spawnattr_t* attr, int policy) {
(*attr)->schedpolicy = policy;
return 0;
}
int posix_spawnattr_getschedpolicy(const posix_spawnattr_t* attr, int* policy) {
*policy = (*attr)->schedpolicy;
return 0;
}
int posix_spawn_file_actions_init(posix_spawn_file_actions_t* actions) {
*actions = reinterpret_cast<__posix_spawn_file_actions*>(calloc(1, sizeof(**actions)));
return (*actions == nullptr) ? errno : 0;
}
int posix_spawn_file_actions_destroy(posix_spawn_file_actions_t* actions) {
__posix_spawn_file_action* a = (*actions)->head;
while (a) {
__posix_spawn_file_action* last = a;
a = a->next;
free(last->path);
free(last);
}
free(*actions);
*actions = nullptr;
return 0;
}
static int posix_spawn_add_file_action(posix_spawn_file_actions_t* actions,
Action what,
int fd,
int new_fd,
const char* path,
int flags,
mode_t mode) {
__posix_spawn_file_action* action =
reinterpret_cast<__posix_spawn_file_action*>(malloc(sizeof(*action)));
if (action == nullptr) return errno;
action->next = nullptr;
if (path != nullptr) {
action->path = strdup(path);
if (action->path == nullptr) {
free(action);
return errno;
}
} else {
action->path = nullptr;
}
action->what = what;
action->fd = fd;
action->new_fd = new_fd;
action->flags = flags;
action->mode = mode;
if ((*actions)->head == nullptr) {
(*actions)->head = (*actions)->last = action;
} else {
(*actions)->last->next = action;
(*actions)->last = action;
}
return 0;
}
int posix_spawn_file_actions_addopen(posix_spawn_file_actions_t* actions,
int fd, const char* path, int flags, mode_t mode) {
if (fd < 0) return EBADF;
return posix_spawn_add_file_action(actions, kOpen, -1, fd, path, flags, mode);
}
int posix_spawn_file_actions_addclose(posix_spawn_file_actions_t* actions, int fd) {
if (fd < 0) return EBADF;
return posix_spawn_add_file_action(actions, kClose, fd, -1, nullptr, 0, 0);
}
int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t* actions, int fd, int new_fd) {
if (fd < 0 || new_fd < 0) return EBADF;
return posix_spawn_add_file_action(actions, kDup2, fd, new_fd, nullptr, 0, 0);
}