[3.13.y-ckt stable] Patch "vfs: Ignore unlocked mounts in fs_fully_visible" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    vfs: Ignore unlocked mounts in fs_fully_visible

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt24.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From bdefaf759d3ff482a3cb4fbd3bc19474a7f253b6 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm at xmission.com>
Date: Wed, 7 Jan 2015 08:10:09 -0600
Subject: 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 at xmission.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/namespace.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index dfe193a..df7bf37 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3031,11 +3031,15 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
 		    ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
 			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)
--
1.9.1