vfs: Don't allow a user namespace root to make device nodes

Safely making device nodes in a container is solvable but simply
having the capability in a user namespace is not sufficient to make
this work.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

diff --git a/fs/namei.c b/fs/namei.c
index 1898198..701954d 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2560,8 +2560,7 @@ int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
        if (error)
                return error;
 
-       if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
-           !ns_capable(inode_userns(dir), CAP_MKNOD))
+       if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
                return -EPERM;
 
        if (!dir->i_op->mknod)