Re: [PATCH v23 16/22] richacl: Create-time inheritance

Jeff Layton
2016-07-12T11:42:02Z

On Thu, 2016-06-30 at 15:47 +0200, Andreas Gruenbacher wrote:
> When a new file is created, it can inherit an acl from its parent
> directory; this is similar to how default acls work in POSIX ACLs.
>
> As with POSIX ACLs, if a file inherits an acl from its parent directory,
> the intersection between the create mode and the permissions granted by
> the inherited acl determines the file masks and file permission bits,
> and the umask is ignored.
>
> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
> ---
>  fs/richacl.c            | 151 ++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/richacl.h |   2 +
>  2 files changed, 153 insertions(+)
>
> diff --git a/fs/richacl.c b/fs/richacl.c
> index e8a383b..29eaf89 100644
> --- a/fs/richacl.c
> +++ b/fs/richacl.c
> @@ -722,3 +722,154 @@ richacl_equiv_mode(const struct richacl *acl, umode_t *mode_p)
>   return 0;
>  }
>  EXPORT_SYMBOL_GPL(richacl_equiv_mode);
> +
> +static inline bool
> +ace_inherits_to_directory(const struct richace *ace)
> +{
> + if (ace->e_flags & RICHACE_DIRECTORY_INHERIT_ACE)
> + return true;
> + if ((ace->e_flags & RICHACE_FILE_INHERIT_ACE) &&
> +     !(ace->e_flags & RICHACE_NO_PROPAGATE_INHERIT_ACE))
> + return true;
> + return false;
> +}
> +
> +/**
> + * richacl_inherit  -  compute the inherited acl of a new file
> + * @dir_acl: acl of the containing directory
> + * @isdir: inherit by a directory or non-directory?
> + *
> + * A directory can have acl entries which files and/or directories created
> + * inside the directory will inherit.  This function computes the acl for such
> + * a new file.  If there is no inheritable acl, it will return %NULL.
> + */
> +struct richacl *
> +richacl_inherit(const struct richacl *dir_acl, int isdir)
> +{
> + const struct richace *dir_ace;
> + struct richacl *acl = NULL;
> + struct richace *ace;
> + int count = 0;
> +
> + if (isdir) {
> + richacl_for_each_entry(dir_ace, dir_acl) {
> + if (!ace_inherits_to_directory(dir_ace))
> + continue;
> + count++;
> + }
> + if (!count)
> + return NULL;
> + acl = richacl_alloc(count, GFP_KERNEL);
> + if (!acl)
> + return ERR_PTR(-ENOMEM);
> + ace = acl->a_entries;
> + richacl_for_each_entry(dir_ace, dir_acl) {
> + if (!ace_inherits_to_directory(dir_ace))
> + continue;
> + richace_copy(ace, dir_ace);
> + if (dir_ace->e_flags & RICHACE_NO_PROPAGATE_INHERIT_ACE)
> + ace->e_flags &= ~RICHACE_INHERITANCE_FLAGS;
> + else if (dir_ace->e_flags & RICHACE_DIRECTORY_INHERIT_ACE)
> + ace->e_flags &= ~RICHACE_INHERIT_ONLY_ACE;
> + else
> + ace->e_flags |= RICHACE_INHERIT_ONLY_ACE;
> + ace++;
> + }
> + } else {
> + richacl_for_each_entry(dir_ace, dir_acl) {
> + if (!(dir_ace->e_flags & RICHACE_FILE_INHERIT_ACE))
> + continue;
> + count++;
> + }
> + if (!count)
> + return NULL;
> + acl = richacl_alloc(count, GFP_KERNEL);
> + if (!acl)
> + return ERR_PTR(-ENOMEM);
> + ace = acl->a_entries;
> + richacl_for_each_entry(dir_ace, dir_acl) {
> + if (!(dir_ace->e_flags & RICHACE_FILE_INHERIT_ACE))
> + continue;
> + richace_copy(ace, dir_ace);
> + ace->e_flags &= ~RICHACE_INHERITANCE_FLAGS;
> + /*
> +  * RICHACE_DELETE_CHILD is meaningless for
> +  * non-directories, so clear it.
> +  */
> + ace->e_mask &= ~RICHACE_DELETE_CHILD;
> + ace++;
> + }
> + }
> +
> + return acl;
> +}
> +
> +/*
> + * richacl_inherit_inode  -  compute inherited acl and file mode
> + * @dir_acl: acl of the containing directory
> + * @mode_p: mode of the new inode
> + *
> + * The file permission bits in @mode_p must be set to the create mode by the
> + * caller.
> + *
> + * If there is an inheritable acl, the maximum permissions that the acl grants
> + * are computed and the file masks of the new acl are set accordingly.
> + */
> +static struct richacl *
> +richacl_inherit_inode(const struct richacl *dir_acl, umode_t *mode_p)
> +{
> + struct richacl *acl;
> + umode_t mode = *mode_p;
> +
> + acl = richacl_inherit(dir_acl, S_ISDIR(mode));
> + if (acl) {
> + if (richacl_equiv_mode(acl, &mode) == 0) {
> + *mode_p &= mode;
> + richacl_put(acl);
> + acl = NULL;
> + } else {
> + richacl_compute_max_masks(acl);
> + /*
> +  * Ensure that the acl will not grant any permissions
> +  * beyond the create mode.
> +  */
> + acl->a_flags |= RICHACL_MASKED;
> + acl->a_owner_mask &=
> + richacl_mode_to_mask(mode >> 6);
> + acl->a_group_mask &=
> + richacl_mode_to_mask(mode >> 3);
> + acl->a_other_mask &=
> + richacl_mode_to_mask(mode);
> + }
> + } else
> + *mode_p &= ~current_umask();
> +
> + return acl;
> +}
> +
> +/**
> + * richacl_create  -  filesystem create helper
> + * @mode_p: mode of the new inode
> + * @dir: containing directory
> + *
> + * Compute the inherited acl for a new inode.  If there is no acl to inherit,
> + * apply the umask.  Use when creating a new inode on a richacl enabled file
> + * system.
> + */
> +struct richacl *richacl_create(umode_t *mode_p, struct inode *dir)
> +{
> + struct richacl *dir_acl, *acl = NULL;
> +
> + if (S_ISLNK(*mode_p))
> + return NULL;
> + dir_acl = get_richacl(dir);
> + if (dir_acl) {
> + if (IS_ERR(dir_acl))
> + return dir_acl;
> + acl = richacl_inherit_inode(dir_acl, mode_p);
> + richacl_put(dir_acl);
> + } else
> + *mode_p &= ~current_umask();
> + return acl;
> +}
> +EXPORT_SYMBOL_GPL(richacl_create);
> diff --git a/include/linux/richacl.h b/include/linux/richacl.h
> index 9212edb..7aca1a3 100644
> --- a/include/linux/richacl.h
> +++ b/include/linux/richacl.h
> @@ -192,5 +192,7 @@ extern void richacl_compute_max_masks(struct richacl *);
>  extern int richacl_permission(struct inode *, const struct richacl *, int);
>  extern int richacl_chmod(struct inode *, umode_t);
>  extern int richacl_equiv_mode(const struct richacl *, umode_t *);
> +extern struct richacl *richacl_inherit(const struct richacl *, int);
> +extern struct richacl *richacl_create(umode_t *, struct inode *);
>
>  #endif /* __RICHACL_H */

Reviewed-by: Jeff Layton <jlayton@redhat.com>