fix ksh-style close-on-exec-for-fds-above-2 in dup-to-self scenario

bugreport by catern via IRC

check.t

@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/check.t,v 1.809 2018/10/20 18:48:26 tg Exp $
+# $MirOS: src/bin/mksh/check.t,v 1.810 2018/12/04 21:13:44 tg Exp $
 # -*- mode: sh -*-
 #-
 # Copyright © 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
@@ -30,7 +30,7 @@
 # (2013/12/02 20:39:44) http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/regress/bin/ksh/?sortby=date
 
 expected-stdout:
-	@(#)MIRBSD KSH R56 2018/10/20
+	@(#)MIRBSD KSH R56 2018/12/04
 description:
 	Check base version of full shell
 stdin:
@@ -39,7 +39,7 @@ name: KSH_VERSION
 category: !shell:legacy-yes
 ---
 expected-stdout:
-	@(#)LEGACY KSH R56 2018/10/20
+	@(#)LEGACY KSH R56 2018/12/04
 description:
 	Check base version of legacy shell
 stdin:
@@ -11264,6 +11264,34 @@ stdin:
 expected-stdout:
 	Fowl
 ---
+name: fd-cloexec-3
+description:
+	Another check for close-on-exec
+stdin:
+	print '#!'"$__progname" >ts
+	cat >>ts <<'EOF'
+	s=ERR
+	read -rN-1 -u$1 s 2>/dev/null; e=$?
+	print -r -- "($1, $((!e)), $s)"
+	EOF
+	chmod +x ts
+	print foo >tx
+	runtest() {
+		s=$1; shift
+		print -r -- $("$__progname" "$@" -c "$s") "$@" .
+	}
+	runtest 'exec 3<tx; ./ts 3 3<&3; ./ts 3'
+	runtest 'exec 3<tx; ./ts 3 3<&3; ./ts 3' -o posix
+	runtest 'exec 3<tx; ./ts 3 3<&3; ./ts 3' -o sh
+	runtest 'exec 3<tx; ./ts 4 4<&3; ./ts 4 4<&3'
+	runtest 'exec 3<tx; ./ts 3 3<&3; ./ts 3 3<&3'
+expected-stdout:
+	(3, 1, foo) (3, 0, ERR) .
+	(3, 1, foo) (3, 1, ) -o posix .
+	(3, 1, foo) (3, 1, ) -o sh .
+	(4, 1, foo) (4, 1, ) .
+	(3, 1, foo) (3, 1, ) .
+---
 name: comsub-1a
 description:
 	COMSUB are now parsed recursively, so this works

exec.c

@@ -2,7 +2,7 @@
 
 /*-
  * Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
- *		 2011, 2012, 2013, 2014, 2015, 2016, 2017
+ *		 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018
  *	mirabilos <m@mirbsd.org>
  *
  * Provided that these terms and disclaimer and all copyright notices
@@ -23,7 +23,7 @@
 
 #include "sh.h"
 
-__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.203 2018/10/30 17:10:14 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.204 2018/12/04 21:13:47 tg Exp $");
 
 #ifndef MKSH_DEFAULT_EXECSHELL
 #define MKSH_DEFAULT_EXECSHELL	MKSH_UNIXROOT "/bin/sh"
@@ -429,6 +429,12 @@ execute(struct op * volatile t,
 		up = makenv();
 		restoresigs();
 		cleanup_proc_env();
+		/* I/O redirection cleanup to be done in child process */
+		if (!Flag(FPOSIX) && !Flag(FSH) && t->left->ioact != NULL)
+			for (iowp = t->left->ioact; *iowp != NULL; iowp++)
+				if ((*iowp)->ioflag & IODUPSELF)
+					fcntl((*iowp)->unit, F_SETFD, 0);
+		/* try to execute */
 		{
 			union mksh_ccphack cargs;
 
@@ -1485,9 +1491,11 @@ iosetup(struct ioword *iop, struct tbl *tp)
 			afree(sp, ATEMP);
 			return (-1);
 		}
-		if (u == (int)iop->unit)
+		if (u == (int)iop->unit) {
 			/* "dup from" == "dup to" */
+			iop->ioflag |= IODUPSELF;
 			return (0);
+		}
 		break;
 	    }
 	}

sh.h

@@ -182,9 +182,9 @@
 #endif
 
 #ifdef EXTERN
-__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.867 2018/10/30 17:10:16 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.868 2018/12/04 21:13:47 tg Exp $");
 #endif
-#define MKSH_VERSION "R56 2018/10/20"
+#define MKSH_VERSION "R56 2018/12/04"
 
 /* arithmetic types: C implementation */
 #if !HAVE_CAN_INTTYPES
@@ -1954,10 +1954,11 @@ struct ioword {
 #define IOSKIP		BIT(5)	/* <<-, skip ^\t* */
 #define IOCLOB		BIT(6)	/* >|, override -o noclobber */
 #define IORDUP		BIT(7)	/* x<&y (as opposed to x>&y) */
-#define IONAMEXP	BIT(8)	/* name has been expanded */
-#define IOBASH		BIT(9)	/* &> etc. */
-#define IOHERESTR	BIT(10)	/* <<< (here string) */
-#define IONDELIM	BIT(11)	/* null delimiter (<<) */
+#define IODUPSELF	BIT(8)	/* x>&x (as opposed to x>&y) */
+#define IONAMEXP	BIT(9)	/* name has been expanded */
+#define IOBASH		BIT(10)	/* &> etc. */
+#define IOHERESTR	BIT(11)	/* <<< (here string) */
+#define IONDELIM	BIT(12)	/* null delimiter (<<) */
 
 /* execute/exchild flags */
 #define XEXEC	BIT(0)		/* execute without forking */