bin/55551: [PATCH] script(1): Minor modification to tcgetattr error handling.

[soumendra%tamu.edu@localhost]

>Number:         55551
>Category:       bin
>Synopsis:       [PATCH] script(1): Minor modification to tcgetattr error handling.
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 08 14:40:00 +0000 2020
>Originator:     Soumendra Ganguly
>Release:        9.0
>Organization:
Texas A&M University
>Environment:
NetBSD localhost 9.0 NetBSD 9.0 (GENERIC) #0: Fri Feb 14 00:06:28 UTC 2020  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
Upon more testing, it was found that the way tcgetattr is called in script(1), it cannot fail with errno == EBADF under normal circumstances (*): script(1) of course does not close its own stdin/stdout voluntarily mid execution.

(*) The only way I was able to force an EBADF was by using
[ p close(1) ] in gdb. Therefore, the EBADF error handling is not removed by this patch, it is only changed to errno != ENOTTY.

>How-To-Repeat:
There is no problem. Only minor restructuring is being done.
>Fix:
--- src/usr.bin/script/script.c	2020-08-08 04:42:52.154774132 -0500
+++ script.c	2020-08-08 04:58:28.624464431 -0500
@@ -158,16 +158,10 @@
 
 	if (tcgetattr(STDIN_FILENO, &tt) == -1 ||
 	    ioctl(STDIN_FILENO, TIOCGWINSZ, &win) == -1) {
-		switch (errno) {
-		case ENOTTY:
-			if (openpty(&master, &slave, NULL, NULL, NULL) == -1)
-				err(EXIT_FAILURE, "openpty");
-			break;
-		case EBADF:
-			err(EXIT_FAILURE, "%d not valid fd", STDIN_FILENO);
-		default: /* errno == EFAULT or EINVAL for ioctl. Not reached in practice. */
-			err(EXIT_FAILURE, "ioctl");
-		}
+		if (errno != ENOTTY) /* For debugger. */
+			err(EXIT_FAILURE, "tcgetattr/ioctl");
+		if (openpty(&master, &slave, NULL, NULL, NULL) == -1)
+			err(EXIT_FAILURE, "openpty");
 	} else {
 		if (openpty(&master, &slave, NULL, &tt, &win) == -1)
 			err(EXIT_FAILURE, "openpty");
@@ -383,9 +377,8 @@
 	struct termios traw;
 
 	if (tcgetattr(STDOUT_FILENO, &tt) == -1) {
-		if (errno == EBADF)
-			err(EXIT_FAILURE, "%d not valid fd", STDOUT_FILENO);
-		/* errno == ENOTTY */
+		if (errno != ENOTTY) /* For debugger. */
+			err(EXIT_FAILURE, "tcgetattr");
 		return;
 	}
 	isterm = 1;