[Devel] [patch -mm 14/17] user namespace: maintain user ns for priv_userns mounts to vfsmount

[clg at fr.ibm.com]

From: Serge E. Hallyn <serue at us.ibm.com>

If a vfsmount is marked priv_userns, then a bind mount should
maintain the old->user_ns.  Not doing so presents a simple way
around the priv_userns security mechanism  :)

Signed-off-by: Serge E. Hallyn <serue at us.ibm.com>
---
 fs/namespace.c |    2 ++
 1 file changed, 2 insertions(+)

Index: 2.6.19-rc6-mm2/fs/namespace.c
===================================================================
--- 2.6.19-rc6-mm2.orig/fs/namespace.c
+++ 2.6.19-rc6-mm2/fs/namespace.c
@@ -240,6 +240,8 @@ static struct vfsmount *clone_mnt(struct
 
 	if (mnt) {
 		mnt->mnt_flags = old->mnt_flags;
+		if (mnt->mnt_flags & MNT_PRIV_USERNS)
+			mnt->mnt_user_ns = old->mnt_user_ns;
 		atomic_inc(&sb->s_active);
 		mnt->mnt_sb = sb;
 		mnt->mnt_root = dget(root);

-- 
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