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rewrite popen to use posix_spawn instead of fragile vfork hacks

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This commit is contained in:
Rich Felker 2013-03-24 22:41:38 -04:00
parent 7914ce9204
commit 9cb6e6ea12
1 changed files with 41 additions and 41 deletions
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82
src/stdio/popen.c
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@ -2,28 +2,23 @@
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <spawn.h>
#include "stdio_impl.h"
#include "pthread_impl.h"
#include "syscall.h"
static void dummy_0()
{
}
weak_alias(dummy_0, __acquire_ptc);
weak_alias(dummy_0, __release_ptc);
pid_t __vfork(void);
extern char **__environ;
FILE *popen(const char *cmd, const char *mode)
{
int p[2], op, i;
int p[2], op, e;
pid_t pid;
FILE *f;
sigset_t old;
const char *modes = "rw", *mi = strchr(modes, *mode);
posix_spawn_file_actions_t fa;
if (mi) {
op = mi-modes;
if (*mode == 'r') {
op = 0;
} else if (*mode == 'w') {
op = 1;
} else {
errno = EINVAL;
return 0;
@ -36,38 +31,43 @@ FILE *popen(const char *cmd, const char *mode)
__syscall(SYS_close, p[1]);
return NULL;
}
FLOCK(f);
sigprocmask(SIG_BLOCK, SIGALL_SET, &old);
__acquire_ptc();
pid = __vfork();
if (pid) {
__release_ptc();
/* If the child's end of the pipe happens to already be on the final
* fd number to which it will be assigned (either 0 or 1), it must
* be moved to a different fd. Otherwise, there is no safe way to
* remove the close-on-exec flag in the child without also creating
* a file descriptor leak race condition in the parent. */
if (p[1-op] == 1-op) {
int tmp = fcntl(F_DUPFD_CLOEXEC, 1-op, 0);
if (tmp < 0) {
e = errno;
goto fail;
}
__syscall(SYS_close, p[1-op]);
sigprocmask(SIG_SETMASK, &old, 0);
if (pid < 0) {
fclose(f);
return 0;
}
f->pipe_pid = pid;
return f;
p[1-op] = tmp;
}
/* See notes in system.c for why this is needed. */
for (i=1; i<=8*__SYSCALL_SSLEN; i++) {
struct sigaction sa;
__libc_sigaction(i, 0, &sa);
if (sa.sa_handler!=SIG_IGN && sa.sa_handler!=SIG_DFL) {
sa.sa_handler = SIG_DFL;
__libc_sigaction(i, &sa, 0);
e = ENOMEM;
if (!posix_spawn_file_actions_init(&fa)) {
if (!posix_spawn_file_actions_adddup2(&fa, p[1-op], 1-op)) {
if (!(e = posix_spawn(&pid, "/bin/sh", &fa, 0,
(char *[]){ "sh", "-c", (char *)cmd, 0 }, __environ))) {
posix_spawn_file_actions_destroy(&fa);
f->pipe_pid = pid;
if (!strchr(mode, 'e'))
fcntl(p[op], F_SETFD, 0);
__syscall(SYS_close, p[1-op]);
FUNLOCK(f);
return f;
}
}
posix_spawn_file_actions_destroy(&fa);
}
if (dup2(p[1-op], 1-op) < 0) _exit(127);
fcntl(1-op, F_SETFD, 0);
if (p[0] != 1-op) __syscall(SYS_close, p[0]);
if (p[1] != 1-op) __syscall(SYS_close, p[1]);
sigprocmask(SIG_SETMASK, &old, 0);
execl("/bin/sh", "sh", "-c", cmd, (char *)0);
_exit(127);
fail:
fclose(f);
__syscall(SYS_close, p[1-op]);
errno = e;
return 0;
}