Re: [PATCH v4 11/16] securityfs: Only use simple_pin_fs/simple_release_fs for init_user_ns

On 12/8/21 06:58, Christian Brauner wrote:

On Tue, Dec 07, 2021 at 03:21:22PM -0500, Stefan Berger wrote:

quoted

To prepare for virtualization of SecurityFS, use simple_pin_fs and
simpe_release_fs only when init_user_ns is active.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
  security/inode.c | 30 +++++++++++++++++++++---------
  1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/security/inode.c b/security/inode.c
index 6c326939750d..1a720b2c566d 100644
--- a/security/inode.c
+++ b/security/inode.c

@@ -21,9 +21,10 @@
  #include <linux/security.h>
  #include <linux/lsm_hooks.h>
  #include <linux/magic.h>
+#include <linux/user_namespace.h>
  
-static struct vfsmount *mount;
-static int mount_count;
+static struct vfsmount *securityfs_mount;
+static int securityfs_mount_count;
  
  static void securityfs_free_inode(struct inode *inode)
  {

@@ -109,6 +110,7 @@ static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
  					const struct file_operations *fops,
  					const struct inode_operations *iops)
  {
+	struct user_namespace *ns = current_user_ns();
  	struct dentry *dentry;
  	struct inode *dir, *inode;
  	int error;

@@ -118,12 +120,17 @@ static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
  
  	pr_debug("securityfs: creating file '%s'\n",name);
  
-	error = simple_pin_fs(&fs_type, &mount, &mount_count);
-	if (error)
-		return ERR_PTR(error);
+	if (ns == &init_user_ns) {
+		error = simple_pin_fs(&fs_type, &securityfs_mount,
+				      &securityfs_mount_count);
+		if (error)
+			return ERR_PTR(error);
+	}
  
-	if (!parent)
-		parent = mount->mnt_root;
+	if (!parent) {
+		if (ns == &init_user_ns)
+			parent = securityfs_mount->mnt_root;

Wouldn't you want an

		else
			return ERR_PTR(-EINVAL);

in here already?

Fixed.