4 files changed, 55 insertions, 23 deletions

diff --git a/lib/libc/stdio/fdopen.c b/lib/libc/stdio/fdopen.c
index 26e2cd70bc1e..8fc90a438b99 100644
--- a/lib/libc/stdio/fdopen.c
+++ b/lib/libc/stdio/fdopen.c
@@ -80,6 +80,12 @@ fdopen(fd, mode)
 
 	if ((fp = __sfp()) == NULL)
 		return (NULL);
+
+	if ((oflags & O_CLOEXEC) && _fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) {
+		fp->_flags = 0;
+		return (NULL);
+	}
+
 	fp->_flags = flags;
 	/*
 	 * If opened for appending, but underlying descriptor does not have
diff --git a/lib/libc/stdio/flags.c b/lib/libc/stdio/flags.c
index 0b6b0755bd3b..d08071dd71b6 100644
--- a/lib/libc/stdio/flags.c
+++ b/lib/libc/stdio/flags.c
@@ -53,7 +53,7 @@ __sflags(mode, optr)
 	const char *mode;
 	int *optr;
 {
-	int ret, m, o;
+	int ret, m, o, known;
 
 	switch (*mode++) {
 
@@ -80,28 +80,34 @@ __sflags(mode, optr)
 		return (0);
 	}
 
-	/* 'b' (binary) is ignored */
-	if (*mode == 'b')
-		mode++;
-
-	/* [rwa][b]\+ means read and write */
-	if (*mode == '+') {
-		mode++;
-		ret = __SRW;
-		m = O_RDWR;
-	}
-
-	/* 'b' (binary) can appear here, too -- and is ignored again */
-	if (*mode == 'b')
-		mode++;
-
-	/* 'x' means exclusive (fail if the file exists) */
-	if (*mode == 'x') {
-		if (m == O_RDONLY) {
-			errno = EINVAL;
-			return (0);
+	do {
+		known = 1;
+		switch (*mode++) {
+		case 'b':
+			/* 'b' (binary) is ignored */
+			break;
+		case '+':
+			/* [rwa][b]\+ means read and write */
+			ret = __SRW;
+			m = O_RDWR;
+			break;
+		case 'x':
+			/* 'x' means exclusive (fail if the file exists) */
+			o |= O_EXCL;
+			break;
+		case 'e':
+			/* set close-on-exec */
+			o |= O_CLOEXEC;
+			break;
+		default:
+			known = 0;
+			break;
 		}
-		o |= O_EXCL;
+	} while (known);
+
+	if ((o & O_EXCL) != 0 && m == O_RDONLY) {
+		errno = EINVAL;
+		return (0);
 	}
 
 	*optr = m | o;
diff --git a/lib/libc/stdio/fopen.3 b/lib/libc/stdio/fopen.3
index 57f5a3dbf88b..f11f4e07e3de 100644
--- a/lib/libc/stdio/fopen.3
+++ b/lib/libc/stdio/fopen.3
@@ -100,6 +100,14 @@ or
 causes the
 .Fn fopen
 call to fail if the file already exists.
+An optional
+.Dq Li e
+following the above
+causes the
+.Fn fopen
+call to set the
+.Dv FD_CLOEXEC
+flag on the underlying file descriptor.
 .Pp
 The
 .Fa mode
@@ -149,6 +157,11 @@ of the stream must be compatible with the mode of the file descriptor.
 The
 .Dq Li x
 mode option is ignored.
+If the
+.Dq Li e
+mode option is present, the
+.Dv FD_CLOEXEC
+flag is set, otherwise it remains unchanged.
 When the stream is closed via
 .Xr fclose 3 ,
 .Fa fildes
@@ -313,6 +326,10 @@ function
 conforms to
 .St -p1003.1-88 .
 The
+.Dq Li e
+mode option does not conform to any standard
+but is also supported by glibc.
+The
 .Fn fmemopen
 function
 conforms to
diff --git a/lib/libc/stdio/freopen.c b/lib/libc/stdio/freopen.c
index be7bc8a2f8d0..8d1ec917086a 100644
--- a/lib/libc/stdio/freopen.c
+++ b/lib/libc/stdio/freopen.c
@@ -118,6 +118,8 @@ freopen(file, mode, fp)
 			(void) ftruncate(fp->_file, (off_t)0);
 		if (!(oflags & O_APPEND))
 			(void) _sseek(fp, (fpos_t)0, SEEK_SET);
+		if (oflags & O_CLOEXEC)
+			(void) _fcntl(fp->_file, F_SETFD, FD_CLOEXEC);
 		f = fp->_file;
 		isopen = 0;
 		wantfd = -1;
@@ -194,7 +196,8 @@ finish:
 	 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
 	 */
 	if (wantfd >= 0) {
-		if (_dup2(f, wantfd) >= 0) {
+		if ((oflags & O_CLOEXEC ? _fcntl(f, F_DUP2FD_CLOEXEC, wantfd) :
+		    _dup2(f, wantfd)) >= 0) {
 			(void)_close(f);
 			f = wantfd;
 		} else