[lxc-devel] [lxd/master] openpty: fix TIOCGPTPEER usage

[brauner on Github]

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From 6f123325150ff49bef6d7d67570a92ce20233b3e Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Tue, 12 May 2020 11:04:53 +0200
Subject: [PATCH] openpty: fix TIOCGPTPEER usage

We made this our controlling terminal which is a bit of an issue.

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 shared/util_linux.go | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/shared/util_linux.go b/shared/util_linux.go
index 4957a312bb..c0e6766c54 100644
--- a/shared/util_linux.go
+++ b/shared/util_linux.go
@@ -415,9 +415,16 @@ func OpenPty(uid, gid int64) (*os.File, *os.File, error) {
 	}
 
 	var slave *os.File
-	slaveFd, err := unix.IoctlRetInt(int(master.Fd()), unix.TIOCGPTPEER)
+	slaveFd, _, err := unix.Syscall(unix.SYS_IOCTL, uintptr(master.Fd()), unix.TIOCGPTPEER, uintptr(unix.O_NOCTTY|unix.O_CLOEXEC|os.O_RDWR))
 	if err == nil {
-		slave = os.NewFile(uintptr(slaveFd), fmt.Sprintf("%d", slaveFd))
+		// Get the slave side.
+		id := 0
+		_, _, errno = unix.Syscall(unix.SYS_IOCTL, uintptr(master.Fd()), unix.TIOCGPTN, uintptr(unsafe.Pointer(&id)))
+		if errno != 0 {
+			return nil, nil, unix.Errno(errno)
+		}
+
+		slave = os.NewFile(uintptr(slaveFd), fmt.Sprintf("/dev/pts/%d", id))
 	} else {
 		// Get the slave side.
 		id := 0