[lxc-devel] [lxd/master] forkmount: ignore ENOENT and EINVAL on umount2()

[brauner on Github]

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From 3663684b5e3975c9d74014982e400141db333000 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Mon, 4 Jun 2018 15:17:47 +0200
Subject: [PATCH] forkmount: ignore ENOENT and EINVAL on umount2()

Closes #4620.

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 lxd/main_forkmount.go | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/lxd/main_forkmount.go b/lxd/main_forkmount.go
index 51591ae99..80bb216ba 100644
--- a/lxd/main_forkmount.go
+++ b/lxd/main_forkmount.go
@@ -155,23 +155,29 @@ void forkdomount(pid_t pid) {
 }
 
 void forkdoumount(pid_t pid) {
+	int ret;
 	char *path = NULL;
 
-	if (dosetns(pid, "mnt") < 0) {
-		fprintf(stderr, "Failed setns to container mount namespace: %s\n", strerror(errno));
+	ret = dosetns(pid, "mnt");
+	if (ret < 0) {
+		fprintf(stderr, "Failed to setns to container mount namespace: %s\n", strerror(errno));
 		_exit(1);
 	}
 
 	path = advance_arg(true);
-	if (access(path, F_OK) < 0) {
-		fprintf(stderr, "Mount path doesn't exist: %s\n", strerror(errno));
-		_exit(1);
-	}
 
-	if (umount2(path, MNT_DETACH) < 0) {
+	ret = umount2(path, MNT_DETACH);
+	if (ret < 0) {
+		// - ENOENT: The user must have unmounted and removed the path.
+		// - EINVAL: The user must have unmounted. Other explanations
+		//           for EINVAL do not apply.
+		if (errno == ENOENT || errno == EINVAL)
+			_exit(0);
+
 		fprintf(stderr, "Error unmounting %s: %s\n", path, strerror(errno));
 		_exit(1);
 	}
+
 	_exit(0);
 }