[lxc-devel] [lxd/master] exec: fix OpenPtyInDevpts()

[brauner on Github]

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From a32272e33376a801165b7bacd56beac40156fc9d Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Thu, 6 Aug 2020 11:29:01 +0200
Subject: [PATCH] exec: fix OpenPtyInDevpts()

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 lxd/instance_exec.go | 5 ++++-
 shared/util_linux.go | 6 +++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/lxd/instance_exec.go b/lxd/instance_exec.go
index 5ca8006228..da59162df3 100644
--- a/lxd/instance_exec.go
+++ b/lxd/instance_exec.go
@@ -132,10 +132,13 @@ func (s *execWs) Do(op *operations.Operation) error {
 	if s.req.Interactive {
 		ttys = make([]*os.File, 1)
 		ptys = make([]*os.File, 1)
-		ptys[0], ttys[0], err = shared.OpenPtyInDevpts(int(s.devptsFd.Fd()), s.rootUid, s.rootGid)
+
 		if s.devptsFd != nil {
+			ptys[0], ttys[0], err = shared.OpenPtyInDevpts(int(s.devptsFd.Fd()), s.rootUid, s.rootGid)
 			s.devptsFd.Close()
 			s.devptsFd = nil
+		} else {
+			ptys[0], ttys[0], err = shared.OpenPty(s.rootUid, s.rootGid)
 		}
 		if err != nil {
 			return err
diff --git a/shared/util_linux.go b/shared/util_linux.go
index eaba564795..ee689dd8aa 100644
--- a/shared/util_linux.go
+++ b/shared/util_linux.go
@@ -439,7 +439,11 @@ func OpenPtyInDevpts(devpts_fd int, uid, gid int64) (*os.File, *os.File, error)
 		}
 
 		pty = os.NewFile(ptyFd, fmt.Sprintf("/dev/pts/%d", id))
-	} else if devpts_fd < 0 {
+	} else {
+		if devpts_fd >= 0 {
+			return nil, nil, fmt.Errorf("TIOCGPTPEER required but not available")
+		}
+
 		// Get the pty side.
 		id := 0
 		_, _, errno = unix.Syscall(unix.SYS_IOCTL, uintptr(ptx.Fd()), unix.TIOCGPTN, uintptr(unsafe.Pointer(&id)))