[hackers] [st][PATCH 1/1] fix a problem that the standard streams are unexpectedly closed

From: Koichi Murase <myoga.murase_AT_gmail.com>
Date: Tue, 24 Aug 2021 06:25:05 +0900

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.

---
 st.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/st.c b/st.c
index ebdf360..a9338e1 100644
--- a/st.c
+++ b/st.c
_AT_@ -793,14 +793,15 @@ ttynew(const char *line, char *cmd, const char *out, char **args)
 		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");
-- 
2.21.3

Received on Mon Aug 23 2021 - 23:25:05 CEST