From: Eric W. Biederman <ebiederm@xmission.com>
Date: Wed, 7 Jan 2015 14:10:09 +0000 (-0600)
Subject: vfs: Ignore unlocked mounts in fs_fully_visible
X-Git-Tag: v3.14.48~7
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cc7fde84c9f0c8f8e62d01ed4c036b51c6b83c34;p=linux

vfs: Ignore unlocked mounts in fs_fully_visible

commit ceeb0e5d39fcdf4dca2c997bf225c7fc49200b37 upstream.

Limit the mounts fs_fully_visible considers to locked mounts.
Unlocked can always be unmounted so considering them adds hassle
but no security benefit.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 2faa7eacb62b..fc99d185a477 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3031,11 +3031,15 @@ bool fs_fully_visible(struct file_system_type *type)
 		if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
 			continue;
 
-		/* This mount is not fully visible if there are any child mounts
-		 * that cover anything except for empty directories.
+		/* This mount is not fully visible if there are any
+		 * locked child mounts that cover anything except for
+		 * empty directories.
 		 */
 		list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
 			struct inode *inode = child->mnt_mountpoint->d_inode;
+			/* Only worry about locked mounts */
+			if (!(mnt->mnt.mnt_flags & MNT_LOCKED))
+				continue;
 			if (!S_ISDIR(inode->i_mode))
 				goto next;
 			if (inode->i_nlink > 2)