[added to the 4.1 stable tree] mnt: If fs_fully_visible fails call put_filesystem.

From: "Eric W. Biederman" <redacted>

This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.

===============

[ Upstream commit 97c1df3e54e811aed484a036a798b4b25d002ecf ]

Add this trivial missing error handling.

Cc: <redacted>
Fixes: 1b852bceb0d1 ("mnt: Refactor the logic for mounting sysfs and proc in a user namespace")
Signed-off-by: "Eric W. Biederman" <redacted>
Signed-off-by: Sasha Levin <redacted>
---
 fs/namespace.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index fce3cc1..2b80129 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c

@@ -2390,8 +2390,10 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
 			mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
 		}
 		if (type->fs_flags & FS_USERNS_VISIBLE) {
-			if (!fs_fully_visible(type, &mnt_flags))
+			if (!fs_fully_visible(type, &mnt_flags)) {
+				put_filesystem(type);
 				return -EPERM;
+			}
 		}
 	}
 

-- 
2.5.0