c0fe5b9da9
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.
38 lines
753 B
C
38 lines
753 B
C
#include <pty.h>
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#include <unistd.h>
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#include <sys/ioctl.h>
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#include <fcntl.h>
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int forkpty(int *m, char *name, const struct termios *tio, const struct winsize *ws)
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{
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int s, t, i, istmp[3]={0};
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pid_t pid;
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if (openpty(m, &s, name, tio, ws) < 0) return -1;
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/* Ensure before forking that we don't exceed fd limit */
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for (i=0; i<3; i++) {
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if (fcntl(i, F_GETFL) < 0) {
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t = fcntl(s, F_DUPFD, i);
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if (t<0) break;
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else if (t!=i) close(t);
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else istmp[i] = 1;
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}
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}
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pid = i==3 ? fork() : -1;
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if (!pid) {
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close(*m);
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setsid();
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ioctl(s, TIOCSCTTY, (char *)0);
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dup2(s, 0);
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dup2(s, 1);
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dup2(s, 2);
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if (s>2) close(s);
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return 0;
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}
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for (i=0; i<3; i++)
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if (istmp[i]) close(i);
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close(s);
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if (pid < 0) close(*m);
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return pid;
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}
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