mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-16 08:00:05 +00:00
434 lines
14 KiB
C
434 lines
14 KiB
C
/* POSIX spawn interface. Linux version.
|
|
Copyright (C) 2016-2020 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <spawn.h>
|
|
#include <fcntl.h>
|
|
#include <paths.h>
|
|
#include <string.h>
|
|
#include <sys/resource.h>
|
|
#include <sys/wait.h>
|
|
#include <sys/param.h>
|
|
#include <sys/mman.h>
|
|
#include <not-cancel.h>
|
|
#include <local-setxid.h>
|
|
#include <shlib-compat.h>
|
|
#include <nptl/pthreadP.h>
|
|
#include <dl-sysdep.h>
|
|
#include <libc-pointer-arith.h>
|
|
#include <ldsodefs.h>
|
|
#include "spawn_int.h"
|
|
|
|
/* The Linux implementation of posix_spawn{p} uses the clone syscall directly
|
|
with CLONE_VM and CLONE_VFORK flags and an allocated stack. The new stack
|
|
and start function solves most the vfork limitation (possible parent
|
|
clobber due stack spilling). The remaining issue are:
|
|
|
|
1. That no signal handlers must run in child context, to avoid corrupting
|
|
parent's state.
|
|
2. The parent must ensure child's stack freeing.
|
|
3. Child must synchronize with parent to enforce 2. and to possible
|
|
return execv issues.
|
|
|
|
The first issue is solved by blocking all signals in child, even
|
|
the NPTL-internal ones (SIGCANCEL and SIGSETXID). The second and
|
|
third issue is done by a stack allocation in parent, and by using a
|
|
field in struct spawn_args where the child can write an error
|
|
code. CLONE_VFORK ensures that the parent does not run until the
|
|
child has either exec'ed successfully or exited. */
|
|
|
|
|
|
/* The Unix standard contains a long explanation of the way to signal
|
|
an error after the fork() was successful. Since no new wait status
|
|
was wanted there is no way to signal an error using one of the
|
|
available methods. The committee chose to signal an error by a
|
|
normal program exit with the exit code 127. */
|
|
#define SPAWN_ERROR 127
|
|
|
|
#ifdef __ia64__
|
|
# define CLONE(__fn, __stackbase, __stacksize, __flags, __args) \
|
|
__clone2 (__fn, __stackbase, __stacksize, __flags, __args, 0, 0, 0)
|
|
#else
|
|
# define CLONE(__fn, __stack, __stacksize, __flags, __args) \
|
|
__clone (__fn, __stack, __flags, __args)
|
|
#endif
|
|
|
|
/* Since ia64 wants the stackbase w/clone2, re-use the grows-up macro. */
|
|
#if _STACK_GROWS_UP || defined (__ia64__)
|
|
# define STACK(__stack, __stack_size) (__stack)
|
|
#elif _STACK_GROWS_DOWN
|
|
# define STACK(__stack, __stack_size) (__stack + __stack_size)
|
|
#endif
|
|
|
|
|
|
struct posix_spawn_args
|
|
{
|
|
sigset_t oldmask;
|
|
const char *file;
|
|
int (*exec) (const char *, char *const *, char *const *);
|
|
const posix_spawn_file_actions_t *fa;
|
|
const posix_spawnattr_t *restrict attr;
|
|
char *const *argv;
|
|
ptrdiff_t argc;
|
|
char *const *envp;
|
|
int xflags;
|
|
int err;
|
|
};
|
|
|
|
/* Older version requires that shell script without shebang definition
|
|
to be called explicitly using /bin/sh (_PATH_BSHELL). */
|
|
static void
|
|
maybe_script_execute (struct posix_spawn_args *args)
|
|
{
|
|
if (SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_15)
|
|
&& (args->xflags & SPAWN_XFLAGS_TRY_SHELL) && errno == ENOEXEC)
|
|
{
|
|
char *const *argv = args->argv;
|
|
ptrdiff_t argc = args->argc;
|
|
|
|
/* Construct an argument list for the shell. */
|
|
char *new_argv[argc + 2];
|
|
new_argv[0] = (char *) _PATH_BSHELL;
|
|
new_argv[1] = (char *) args->file;
|
|
if (argc > 1)
|
|
memcpy (new_argv + 2, argv + 1, argc * sizeof (char *));
|
|
else
|
|
new_argv[2] = NULL;
|
|
|
|
/* Execute the shell. */
|
|
args->exec (new_argv[0], new_argv, args->envp);
|
|
}
|
|
}
|
|
|
|
/* Function used in the clone call to setup the signals mask, posix_spawn
|
|
attributes, and file actions. It run on its own stack (provided by the
|
|
posix_spawn call). */
|
|
static int
|
|
__spawni_child (void *arguments)
|
|
{
|
|
struct posix_spawn_args *args = arguments;
|
|
const posix_spawnattr_t *restrict attr = args->attr;
|
|
const posix_spawn_file_actions_t *file_actions = args->fa;
|
|
|
|
/* The child must ensure that no signal handler are enabled because it shared
|
|
memory with parent, so the signal disposition must be either SIG_DFL or
|
|
SIG_IGN. It does by iterating over all signals and although it could
|
|
possibly be more optimized (by tracking which signal potentially have a
|
|
signal handler), it might requires system specific solutions (since the
|
|
sigset_t data type can be very different on different architectures). */
|
|
struct sigaction sa;
|
|
memset (&sa, '\0', sizeof (sa));
|
|
|
|
sigset_t hset;
|
|
__sigprocmask (SIG_BLOCK, 0, &hset);
|
|
for (int sig = 1; sig < _NSIG; ++sig)
|
|
{
|
|
if ((attr->__flags & POSIX_SPAWN_SETSIGDEF)
|
|
&& __sigismember (&attr->__sd, sig))
|
|
{
|
|
sa.sa_handler = SIG_DFL;
|
|
}
|
|
else if (__sigismember (&hset, sig))
|
|
{
|
|
if (__is_internal_signal (sig))
|
|
sa.sa_handler = SIG_IGN;
|
|
else
|
|
{
|
|
__libc_sigaction (sig, 0, &sa);
|
|
if (sa.sa_handler == SIG_IGN)
|
|
continue;
|
|
sa.sa_handler = SIG_DFL;
|
|
}
|
|
}
|
|
else
|
|
continue;
|
|
|
|
__libc_sigaction (sig, &sa, 0);
|
|
}
|
|
|
|
#ifdef _POSIX_PRIORITY_SCHEDULING
|
|
/* Set the scheduling algorithm and parameters. */
|
|
if ((attr->__flags & (POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER))
|
|
== POSIX_SPAWN_SETSCHEDPARAM)
|
|
{
|
|
if (__sched_setparam (0, &attr->__sp) == -1)
|
|
goto fail;
|
|
}
|
|
else if ((attr->__flags & POSIX_SPAWN_SETSCHEDULER) != 0)
|
|
{
|
|
if (__sched_setscheduler (0, attr->__policy, &attr->__sp) == -1)
|
|
goto fail;
|
|
}
|
|
#endif
|
|
|
|
if ((attr->__flags & POSIX_SPAWN_SETSID) != 0
|
|
&& __setsid () < 0)
|
|
goto fail;
|
|
|
|
/* Set the process group ID. */
|
|
if ((attr->__flags & POSIX_SPAWN_SETPGROUP) != 0
|
|
&& __setpgid (0, attr->__pgrp) != 0)
|
|
goto fail;
|
|
|
|
/* Set the effective user and group IDs. */
|
|
if ((attr->__flags & POSIX_SPAWN_RESETIDS) != 0
|
|
&& (local_seteuid (__getuid ()) != 0
|
|
|| local_setegid (__getgid ()) != 0))
|
|
goto fail;
|
|
|
|
/* Execute the file actions. */
|
|
if (file_actions != 0)
|
|
{
|
|
int cnt;
|
|
struct rlimit64 fdlimit;
|
|
bool have_fdlimit = false;
|
|
|
|
for (cnt = 0; cnt < file_actions->__used; ++cnt)
|
|
{
|
|
struct __spawn_action *action = &file_actions->__actions[cnt];
|
|
|
|
switch (action->tag)
|
|
{
|
|
case spawn_do_close:
|
|
if (__close_nocancel (action->action.close_action.fd) != 0)
|
|
{
|
|
if (!have_fdlimit)
|
|
{
|
|
__getrlimit64 (RLIMIT_NOFILE, &fdlimit);
|
|
have_fdlimit = true;
|
|
}
|
|
|
|
/* Signal errors only for file descriptors out of range. */
|
|
if (action->action.close_action.fd < 0
|
|
|| action->action.close_action.fd >= fdlimit.rlim_cur)
|
|
goto fail;
|
|
}
|
|
break;
|
|
|
|
case spawn_do_open:
|
|
{
|
|
/* POSIX states that if fildes was already an open file descriptor,
|
|
it shall be closed before the new file is opened. This avoid
|
|
pontential issues when posix_spawn plus addopen action is called
|
|
with the process already at maximum number of file descriptor
|
|
opened and also for multiple actions on single-open special
|
|
paths (like /dev/watchdog). */
|
|
__close_nocancel (action->action.open_action.fd);
|
|
|
|
int ret = __open_nocancel (action->action.open_action.path,
|
|
action->action.
|
|
open_action.oflag | O_LARGEFILE,
|
|
action->action.open_action.mode);
|
|
|
|
if (ret == -1)
|
|
goto fail;
|
|
|
|
int new_fd = ret;
|
|
|
|
/* Make sure the desired file descriptor is used. */
|
|
if (ret != action->action.open_action.fd)
|
|
{
|
|
if (__dup2 (new_fd, action->action.open_action.fd)
|
|
!= action->action.open_action.fd)
|
|
goto fail;
|
|
|
|
if (__close_nocancel (new_fd) != 0)
|
|
goto fail;
|
|
}
|
|
}
|
|
break;
|
|
|
|
case spawn_do_dup2:
|
|
/* Austin Group issue #411 requires adddup2 action with source
|
|
and destination being equal to remove close-on-exec flag. */
|
|
if (action->action.dup2_action.fd
|
|
== action->action.dup2_action.newfd)
|
|
{
|
|
int fd = action->action.dup2_action.newfd;
|
|
int flags = __fcntl (fd, F_GETFD, 0);
|
|
if (flags == -1)
|
|
goto fail;
|
|
if (__fcntl (fd, F_SETFD, flags & ~FD_CLOEXEC) == -1)
|
|
goto fail;
|
|
}
|
|
else if (__dup2 (action->action.dup2_action.fd,
|
|
action->action.dup2_action.newfd)
|
|
!= action->action.dup2_action.newfd)
|
|
goto fail;
|
|
break;
|
|
|
|
case spawn_do_chdir:
|
|
if (__chdir (action->action.chdir_action.path) != 0)
|
|
goto fail;
|
|
break;
|
|
|
|
case spawn_do_fchdir:
|
|
if (__fchdir (action->action.fchdir_action.fd) != 0)
|
|
goto fail;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Set the initial signal mask of the child if POSIX_SPAWN_SETSIGMASK
|
|
is set, otherwise restore the previous one. */
|
|
__sigprocmask (SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
|
|
? &attr->__ss : &args->oldmask, 0);
|
|
|
|
args->exec (args->file, args->argv, args->envp);
|
|
|
|
/* This is compatibility function required to enable posix_spawn run
|
|
script without shebang definition for older posix_spawn versions
|
|
(2.15). */
|
|
maybe_script_execute (args);
|
|
|
|
fail:
|
|
/* errno should have an appropriate non-zero value; otherwise,
|
|
there's a bug in glibc or the kernel. For lack of an error code
|
|
(EINTERNALBUG) describing that, use ECHILD. Another option would
|
|
be to set args->err to some negative sentinel and have the parent
|
|
abort(), but that seems needlessly harsh. */
|
|
args->err = errno ? : ECHILD;
|
|
_exit (SPAWN_ERROR);
|
|
}
|
|
|
|
/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
|
|
Before running the process perform the actions described in FILE-ACTIONS. */
|
|
static int
|
|
__spawnix (pid_t * pid, const char *file,
|
|
const posix_spawn_file_actions_t * file_actions,
|
|
const posix_spawnattr_t * attrp, char *const argv[],
|
|
char *const envp[], int xflags,
|
|
int (*exec) (const char *, char *const *, char *const *))
|
|
{
|
|
pid_t new_pid;
|
|
struct posix_spawn_args args;
|
|
int ec;
|
|
|
|
/* To avoid imposing hard limits on posix_spawn{p} the total number of
|
|
arguments is first calculated to allocate a mmap to hold all possible
|
|
values. */
|
|
ptrdiff_t argc = 0;
|
|
/* Linux allows at most max (0x7FFFFFFF, 1/4 stack size) arguments
|
|
to be used in a execve call. We limit to INT_MAX minus one due the
|
|
compatiblity code that may execute a shell script (maybe_script_execute)
|
|
where it will construct another argument list with an additional
|
|
argument. */
|
|
ptrdiff_t limit = INT_MAX - 1;
|
|
while (argv[argc++] != NULL)
|
|
if (argc == limit)
|
|
{
|
|
errno = E2BIG;
|
|
return errno;
|
|
}
|
|
|
|
int prot = (PROT_READ | PROT_WRITE
|
|
| ((GL (dl_stack_flags) & PF_X) ? PROT_EXEC : 0));
|
|
|
|
/* Add a slack area for child's stack. */
|
|
size_t argv_size = (argc * sizeof (void *)) + 512;
|
|
/* We need at least a few pages in case the compiler's stack checking is
|
|
enabled. In some configs, it is known to use at least 24KiB. We use
|
|
32KiB to be "safe" from anything the compiler might do. Besides, the
|
|
extra pages won't actually be allocated unless they get used. */
|
|
argv_size += (32 * 1024);
|
|
size_t stack_size = ALIGN_UP (argv_size, GLRO(dl_pagesize));
|
|
void *stack = __mmap (NULL, stack_size, prot,
|
|
MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
|
|
if (__glibc_unlikely (stack == MAP_FAILED))
|
|
return errno;
|
|
|
|
/* Disable asynchronous cancellation. */
|
|
int state;
|
|
__libc_ptf_call (__pthread_setcancelstate,
|
|
(PTHREAD_CANCEL_DISABLE, &state), 0);
|
|
|
|
/* Child must set args.err to something non-negative - we rely on
|
|
the parent and child sharing VM. */
|
|
args.err = 0;
|
|
args.file = file;
|
|
args.exec = exec;
|
|
args.fa = file_actions;
|
|
args.attr = attrp ? attrp : &(const posix_spawnattr_t) { 0 };
|
|
args.argv = argv;
|
|
args.argc = argc;
|
|
args.envp = envp;
|
|
args.xflags = xflags;
|
|
|
|
__libc_signal_block_all (&args.oldmask);
|
|
|
|
/* The clone flags used will create a new child that will run in the same
|
|
memory space (CLONE_VM) and the execution of calling thread will be
|
|
suspend until the child calls execve or _exit.
|
|
|
|
Also since the calling thread execution will be suspend, there is not
|
|
need for CLONE_SETTLS. Although parent and child share the same TLS
|
|
namespace, there will be no concurrent access for TLS variables (errno
|
|
for instance). */
|
|
new_pid = CLONE (__spawni_child, STACK (stack, stack_size), stack_size,
|
|
CLONE_VM | CLONE_VFORK | SIGCHLD, &args);
|
|
|
|
/* It needs to collect the case where the auxiliary process was created
|
|
but failed to execute the file (due either any preparation step or
|
|
for execve itself). */
|
|
if (new_pid > 0)
|
|
{
|
|
/* Also, it handles the unlikely case where the auxiliary process was
|
|
terminated before calling execve as if it was successfully. The
|
|
args.err is set to 0 as default and changed to a positive value
|
|
only in case of failure, so in case of premature termination
|
|
due a signal args.err will remain zeroed and it will be up to
|
|
caller to actually collect it. */
|
|
ec = args.err;
|
|
if (ec > 0)
|
|
/* There still an unlikely case where the child is cancelled after
|
|
setting args.err, due to a positive error value. Also there is
|
|
possible pid reuse race (where the kernel allocated the same pid
|
|
to an unrelated process). Unfortunately due synchronization
|
|
issues where the kernel might not have the process collected
|
|
the waitpid below can not use WNOHANG. */
|
|
__waitpid (new_pid, NULL, 0);
|
|
}
|
|
else
|
|
ec = -new_pid;
|
|
|
|
__munmap (stack, stack_size);
|
|
|
|
if ((ec == 0) && (pid != NULL))
|
|
*pid = new_pid;
|
|
|
|
__libc_signal_restore_set (&args.oldmask);
|
|
|
|
__libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0);
|
|
|
|
return ec;
|
|
}
|
|
|
|
/* Spawn a new process executing PATH with the attributes describes in *ATTRP.
|
|
Before running the process perform the actions described in FILE-ACTIONS. */
|
|
int
|
|
__spawni (pid_t * pid, const char *file,
|
|
const posix_spawn_file_actions_t * acts,
|
|
const posix_spawnattr_t * attrp, char *const argv[],
|
|
char *const envp[], int xflags)
|
|
{
|
|
/* It uses __execvpex to avoid run ENOEXEC in non compatibility mode (it
|
|
will be handled by maybe_script_execute). */
|
|
return __spawnix (pid, file, acts, attrp, argv, envp, xflags,
|
|
xflags & SPAWN_XFLAGS_USE_PATH ? __execvpex :__execve);
|
|
}
|