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-Url: https://git.stricted.de/?a=commitdiff_plain;h=ceeb0e5d39fcdf4dca2c997bf225c7fc49200b37;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

vfs: Ignore unlocked mounts in fs_fully_visible

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

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 63b9806235e6..8c7b8e0941b9 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3205,11 +3205,15 @@ 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)