we cannot report failure after forking, so the idea is to ensure prior
to fork that fd 0,1,2 exist. this will prevent dup2 from possibly
hitting a resource limit and failing in the child process. fcntl
rather than dup2 is used prior to forking to avoid race conditions.
#include <pty.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <pty.h>
#include <unistd.h>
#include <sys/ioctl.h>
int forkpty(int *m, char *name, const struct termios *tio, const struct winsize *ws)
{
int forkpty(int *m, char *name, const struct termios *tio, const struct winsize *ws)
{
+ int s, t, i, istmp[3]={0};
pid_t pid;
if (openpty(m, &s, name, tio, ws) < 0) return -1;
pid_t pid;
if (openpty(m, &s, name, tio, ws) < 0) return -1;
+
+ /* Ensure before forking that we don't exceed fd limit */
+ for (i=0; i<3; i++) {
+ if (fcntl(i, F_GETFL) < 0) {
+ t = fcntl(s, F_DUPFD, i);
+ if (t<0) break;
+ else if (t!=i) close(t);
+ else istmp[i] = 1;
+ }
+ }
+ pid = i==3 ? fork() : -1;
if (!pid) {
close(*m);
setsid();
if (!pid) {
close(*m);
setsid();
if (s>2) close(s);
return 0;
}
if (s>2) close(s);
return 0;
}
+ for (i=0; i<3; i++)
+ if (istmp[i]) close(i);
close(s);
if (pid < 0) close(*m);
return pid;
close(s);
if (pid < 0) close(*m);
return pid;