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

[Jeff Layton <jlayton@redhat.com>]

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>

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