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Use dup3() instead of dup2().

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This is less error prone since dup3() returns an error if old == new.
Sudo guarantees that fds 0-2 are already open.
This commit is contained in:
Todd C. Miller
2019-11-02 10:55:50 -06:00
parent 43df086186
commit 356287557f
4 changed files with 35 additions and 46 deletions
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39
src/exec_monitor.c
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@@ -404,33 +404,18 @@ exec_cmnd_pty(struct command_details *details, bool foreground, int errfd)
setpgid(0, self);
/* Wire up standard fds, note that stdout/stderr may be pipes. */
if (io_fds[SFD_STDIN] != STDIN_FILENO) {
if (dup2(io_fds[SFD_STDIN], STDIN_FILENO) == -1)
sudo_fatal("dup2");
if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE])
close(io_fds[SFD_STDIN]);
} else {
if (fcntl(io_fds[SFD_STDIN], F_SETFD, 0) == -1)
sudo_fatal("fcntl");
}
if (io_fds[SFD_STDOUT] != STDOUT_FILENO) {
if (dup2(io_fds[SFD_STDOUT], STDOUT_FILENO) == -1)
sudo_fatal("dup2");
if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE])
close(io_fds[SFD_STDOUT]);
} else {
if (fcntl(io_fds[SFD_STDOUT], F_SETFD, 0) == -1)
sudo_fatal("fcntl");
}
if (io_fds[SFD_STDERR] != STDERR_FILENO) {
if (dup2(io_fds[SFD_STDERR], STDERR_FILENO) == -1)
sudo_fatal("dup2");
if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE])
close(io_fds[SFD_STDERR]);
} else {
if (fcntl(io_fds[SFD_STDERR], F_SETFD, 0) == -1)
sudo_fatal("fcntl");
}
if (dup3(io_fds[SFD_STDIN], STDIN_FILENO, 0) == -1)
sudo_fatal("dup3");
if (io_fds[SFD_STDIN] != io_fds[SFD_SLAVE])
close(io_fds[SFD_STDIN]);
if (dup3(io_fds[SFD_STDOUT], STDOUT_FILENO, 0) == -1)
sudo_fatal("dup3");
if (io_fds[SFD_STDOUT] != io_fds[SFD_SLAVE])
close(io_fds[SFD_STDOUT]);
if (dup3(io_fds[SFD_STDERR], STDERR_FILENO, 0) == -1)
sudo_fatal("dup3");
if (io_fds[SFD_STDERR] != io_fds[SFD_SLAVE])
close(io_fds[SFD_STDERR]);
/* Wait for parent to grant us the tty if we are foreground. */
if (foreground && !ISSET(details->flags, CD_EXEC_BG)) {