commit 1d3142da968da7f6f61f1c1708f39ca233eda150
from: Koichi Murase <myoga.murase@gmail.com>
via: Hiltjo Posthuma <hiltjo@codemadness.org>
date: Tue Aug 24 11:30:11 2021 UTC

fix a problem that the standard streams are unexpectedly closed

In the current implementation, the slave PTY (assigned to the variable
`s') is always closed after duplicating it to file descriptors of
standard streams (0, 1, and 2).  However, when the allocated slave PTY
`s' is already one of 0, 1, or 2, this causes unexpected closing of a
standard stream.  The same problem occurs when the file descriptor of
the master PTY (the variable `m') is one of 0, 1, or 2.

In this patch, the original master PTY (m) is closed before it would
be overwritten by duplicated slave PTYs.  The original slave PTY (s)
is closed only when it is not one of the stanrad streams.

commit - 2ec571a30c0c3b1a17f6b3631c80d573582f59a1
commit + 1d3142da968da7f6f61f1c1708f39ca233eda150
blob - ebdf3609b6a8eb6605791a91894868175b0ecc86
blob + a9338e1a5771762cd0e53fb2f215dccd3378737e
--- st.c
+++ st.c
@@ -793,14 +793,15 @@ ttynew(const char *line, char *cmd, const char *out, c
 		break;
 	case 0:
 		close(iofd);
+		close(m);
 		setsid(); /* create a new process group */
 		dup2(s, 0);
 		dup2(s, 1);
 		dup2(s, 2);
 		if (ioctl(s, TIOCSCTTY, NULL) < 0)
 			die("ioctl TIOCSCTTY failed: %s\n", strerror(errno));
-		close(s);
-		close(m);
+		if (s > 2)
+			close(s);
 #ifdef __OpenBSD__
 		if (pledge("stdio getpw proc exec", NULL) == -1)
 			die("pledge\n");