On Tue, 2022-01-25 at 17:46 -0500, Stefan Berger wrote: > From: Stefan Berger <stefanb@xxxxxxxxxxxxx> > > Enable multiple instances of securityfs by keying each instance with a > pointer to the user namespace it belongs to. > > Since we do not need the pinning of the filesystem for the virtualization > case, limit the usage of simple_pin_fs() and simpe_release_fs() to the > case when the init_user_ns is active. This simplifies the cleanup for the > virtualization case where usage of securityfs_remove() to free dentries > is not needed anymore. Could you add a sentence here explaining why securityfs_remove() isn't needed in the virtualization case? > > For the initial securityfs, i.e. the one mounted in the host userns mount, > nothing changes. The rules for securityfs_remove() are as before and it is > still paired with securityfs_create(). Specifically, a file created via > securityfs_create_dentry() in the initial securityfs mount still needs to > be removed by a call to securityfs_remove(). Creating a new dentry in the > initial securityfs mount still pins the filesystem like it always did. > Consequently, the initial securityfs mount is not destroyed on > umount/shutdown as long as at least one user of it still has dentries that > it hasn't removed with a call to securityfs_remove(). > > Prevent mounting of an instance of securityfs in another user namespace > than it belongs to. Also, prevent accesses to files and directories by > a user namespace that is neither the user namespace it belongs to > nor an ancestor of the user namespace that the instance of securityfs > belongs to. Do not prevent access if securityfs was bind-mounted and > therefore the init_user_ns is the owning user namespace. > > Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx> > Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> > Suggested-by: Christian Brauner <brauner@xxxxxxxxxx> Really nice! A minor nit is that "Suggested-by" should go before your "Signed-off-by". Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
