On Thu, 22 Sept 2022 at 17:18, Christian Brauner <brauner@xxxxxxxxxx> wrote: > > The current way of setting and getting posix acls through the generic > xattr interface is error prone and type unsafe. The vfs needs to > interpret and fixup posix acls before storing or reporting it to > userspace. Various hacks exist to make this work. The code is hard to > understand and difficult to maintain in it's current form. Instead of > making this work by hacking posix acls through xattr handlers we are > building a dedicated posix acl api around the get and set inode > operations. This removes a lot of hackiness and makes the codepaths > easier to maintain. A lot of background can be found in [1]. > > In order to build a type safe posix api around get and set acl we need > all filesystem to implement get and set acl. > > Now that we have added get and set acl inode operations that allow easy > access to the dentry we give overlayfs it's own get and set acl inode > operations. > > Since overlayfs is a stacking filesystem it will use the newly added > posix acl api when retrieving posix acls from the relevant layer. > > Since overlayfs can also be mounted on top of idmapped layers. If > idmapped layers are used overlayfs must take the layer's idmapping into > account after it retrieved the posix acls from the relevant layer. > > Note, until the vfs has been switched to the new posix acl api this > patch is a non-functional change. > > Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@xxxxxxxxxx [1] > Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> > --- > fs/overlayfs/dir.c | 3 +- > fs/overlayfs/inode.c | 63 ++++++++++++++++++++++++++++++++++++---- > fs/overlayfs/overlayfs.h | 10 +++++-- > 3 files changed, 67 insertions(+), 9 deletions(-) > > diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c > index 7bece7010c00..eb49d5d7b56f 100644 > --- a/fs/overlayfs/dir.c > +++ b/fs/overlayfs/dir.c > @@ -1311,7 +1311,8 @@ const struct inode_operations ovl_dir_inode_operations = { > .permission = ovl_permission, > .getattr = ovl_getattr, > .listxattr = ovl_listxattr, > - .get_inode_acl = ovl_get_acl, > + .get_inode_acl = ovl_get_inode_acl, > + .get_acl = ovl_get_acl, > .update_time = ovl_update_time, > .fileattr_get = ovl_fileattr_get, > .fileattr_set = ovl_fileattr_set, > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > index ecb51c249466..dd11e13cd288 100644 > --- a/fs/overlayfs/inode.c > +++ b/fs/overlayfs/inode.c > @@ -14,6 +14,8 @@ > #include <linux/fileattr.h> > #include <linux/security.h> > #include <linux/namei.h> > +#include <linux/posix_acl.h> > +#include <linux/posix_acl_xattr.h> > #include "overlayfs.h" > > > @@ -460,9 +462,9 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size) > * of the POSIX ACLs retrieved from the lower layer to this function to not > * alter the POSIX ACLs for the underlying filesystem. > */ > -static void ovl_idmap_posix_acl(struct inode *realinode, > - struct user_namespace *mnt_userns, > - struct posix_acl *acl) > +void ovl_idmap_posix_acl(struct inode *realinode, > + struct user_namespace *mnt_userns, > + struct posix_acl *acl) > { > struct user_namespace *fs_userns = i_user_ns(realinode); > > @@ -495,7 +497,7 @@ static void ovl_idmap_posix_acl(struct inode *realinode, > * > * This is obviously only relevant when idmapped layers are used. > */ > -struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu) > +struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type, bool rcu) > { > struct inode *realinode = ovl_inode_real(inode); > struct posix_acl *acl, *clone; > @@ -547,6 +549,53 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu) > posix_acl_release(acl); > return clone; > } > + > +static struct posix_acl *ovl_get_acl_path(const struct path *path, > + const char *acl_name) > +{ > + struct posix_acl *real_acl, *clone; > + struct user_namespace *mnt_userns; > + > + mnt_userns = mnt_user_ns(path->mnt); > + > + real_acl = vfs_get_acl(mnt_userns, path->dentry, acl_name); > + if (IS_ERR(real_acl)) > + return real_acl; > + if (!real_acl) > + return NULL; if (IS_ERR_OR_NULL(real_acl)) return real_acl; > + > + if (!is_idmapped_mnt(path->mnt)) > + return real_acl; > + > + /* > + * We cannot alter the ACLs returned from the relevant layer as that > + * would alter the cached values filesystem wide for the lower > + * filesystem. Instead we can clone the ACLs and then apply the > + * relevant idmapping of the layer. > + */ Can't vfs_get_acl() return 'const posix_acl *' to enforce that? Thanks, Miklos
