Re: [PATCH v23 07/22] richacl: Permission mapping functions

[Jeff Layton <jlayton@redhat.com>]

On Thu, 2016-06-30 at 15:46 +0200, Andreas Gruenbacher wrote:
> We need to map from POSIX permissions to NFSv4 permissions when a
> chmod() is done, from NFSv4 permissions to POSIX permissions when an acl
> is set (which implicitly sets the file permission bits), and from the
> MAY_READ/MAY_WRITE/MAY_EXEC/MAY_APPEND flags to NFSv4 permissions when
> doing an access check in a richacl.
> 
> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
> Reviewed-by: J. Bruce Fields <bfields@redhat.com>
> ---
>  fs/richacl.c                 | 118 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/richacl.h      |   3 ++
>  include/uapi/linux/richacl.h |  44 ++++++++++++++++
>  3 files changed, 165 insertions(+)
> 
> diff --git a/fs/richacl.c b/fs/richacl.c
> index bcc6591..d0a4135 100644
> --- a/fs/richacl.c
> +++ b/fs/richacl.c
> @@ -63,3 +63,121 @@ richace_copy(struct richace *to, const struct richace *from)
>  {
>  	memcpy(to, from, sizeof(struct richace));
>  }
> +
> +/*
> + * richacl_mask_to_mode  -  compute the file permission bits from mask
> + * @mask:	%RICHACE_* permission mask
> + *
> + * Compute the file permission bits corresponding to a particular set of
> + * richacl permissions.
> + *
> + * See richacl_masks_to_mode().
> + */
> +static int
> +richacl_mask_to_mode(unsigned int mask)
> +{
> +	int mode = 0;
> +
> +	if (mask & RICHACE_POSIX_MODE_READ)
> +		mode |= S_IROTH;
> +	if (mask & RICHACE_POSIX_MODE_WRITE)
> +		mode |= S_IWOTH;
> +	if (mask & RICHACE_POSIX_MODE_EXEC)
> +		mode |= S_IXOTH;
> +
> +	return mode;
> +}
> +
> +/**
> + * richacl_masks_to_mode  -  compute file permission bits from file masks
> + *
> + * When setting a richacl, we set the file permission bits to indicate maximum
> + * permissions: for example, we set the Write permission when a mask contains
> + * RICHACE_APPEND_DATA even if it does not also contain RICHACE_WRITE_DATA.
> + *
> + * Permissions which are not in RICHACE_POSIX_MODE_READ,
> + * RICHACE_POSIX_MODE_WRITE, or RICHACE_POSIX_MODE_EXEC cannot be represented
> + * in the file permission bits.  Such permissions can still be effective, but
> + * not for new files or after a chmod(); they must be explicitly enabled in the
> + * richacl.
> + */
> +int
> +richacl_masks_to_mode(const struct richacl *acl)
> +{
> +	return richacl_mask_to_mode(acl->a_owner_mask) << 6 |
> +	       richacl_mask_to_mode(acl->a_group_mask) << 3 |
> +	       richacl_mask_to_mode(acl->a_other_mask);
> +}
> +EXPORT_SYMBOL_GPL(richacl_masks_to_mode);
> +
> +/**
> + * richacl_mode_to_mask  - compute a file mask from the lowest three mode bits
> + * @mode:	mode to convert to richacl permissions
> + *
> + * When the file permission bits of a file are set with chmod(), this specifies
> + * the maximum permissions that processes will get.  All permissions beyond
> + * that will be removed from the file masks, and become ineffective.
> + */
> +unsigned int
> +richacl_mode_to_mask(umode_t mode)
> +{
> +	unsigned int mask = 0;
> +
> +	if (mode & S_IROTH)
> +		mask |= RICHACE_POSIX_MODE_READ;
> +	if (mode & S_IWOTH)
> +		mask |= RICHACE_POSIX_MODE_WRITE;
> +	if (mode & S_IXOTH)
> +		mask |= RICHACE_POSIX_MODE_EXEC;
> +
> +	return mask;
> +}
> +
> +/**
> + * richacl_want_to_mask  - convert the iop->permission want argument to a mask
> + * @want:	@want argument of the permission inode operation
> + *
> + * When checking for append, @want is (MAY_WRITE | MAY_APPEND).
> + *
> + * Richacls use the iop->may_create and iop->may_delete hooks which are used
> + * for checking if creating and deleting files is allowed.  These hooks do not
> + * use richacl_want_to_mask(), so we do not have to deal with mapping MAY_WRITE
> + * to RICHACE_ADD_FILE, RICHACE_ADD_SUBDIRECTORY, and RICHACE_DELETE_CHILD
> + * here.
> + */

This comment is confusing as I don't see any may_create or may_delete
iops in the final patchset. Do you mean may_create() and may_delete()
here?

> +unsigned int
> +richacl_want_to_mask(unsigned int want)
> +{
> +	unsigned int mask = 0;
> +
> +	if (want & MAY_READ)
> +		mask |= RICHACE_READ_DATA;
> +	if (want & MAY_DELETE_SELF)
> +		mask |= RICHACE_DELETE;
> +	if (want & MAY_TAKE_OWNERSHIP)
> +		mask |= RICHACE_WRITE_OWNER;
> +	if (want & MAY_CHMOD)
> +		mask |= RICHACE_WRITE_ACL;
> +	if (want & MAY_SET_TIMES)
> +		mask |= RICHACE_WRITE_ATTRIBUTES;
> +	if (want & MAY_EXEC)
> +		mask |= RICHACE_EXECUTE;
> +	/*
> +	 * differentiate MAY_WRITE from these request
> +	 */
> +	if (want & (MAY_APPEND |
> +		    MAY_CREATE_FILE | MAY_CREATE_DIR |
> +		    MAY_DELETE_CHILD)) {
> +		if (want & MAY_APPEND)
> +			mask |= RICHACE_APPEND_DATA;
> +		if (want & MAY_CREATE_FILE)
> +			mask |= RICHACE_ADD_FILE;
> +		if (want & MAY_CREATE_DIR)
> +			mask |= RICHACE_ADD_SUBDIRECTORY;
> +		if (want & MAY_DELETE_CHILD)
> +			mask |= RICHACE_DELETE_CHILD;
> +	} else if (want & MAY_WRITE)
> +		mask |= RICHACE_WRITE_DATA;
> +	return mask;
> +}
> +EXPORT_SYMBOL_GPL(richacl_want_to_mask);
> diff --git a/include/linux/richacl.h b/include/linux/richacl.h
> index edb8480..9102ef0 100644
> --- a/include/linux/richacl.h
> +++ b/include/linux/richacl.h
> @@ -175,5 +175,8 @@ richace_is_same_identifier(const struct richace *a, const struct richace *b)
>  extern struct richacl *richacl_alloc(int, gfp_t);
>  extern struct richacl *richacl_clone(const struct richacl *, gfp_t);
>  extern void richace_copy(struct richace *, const struct richace *);
> +extern int richacl_masks_to_mode(const struct richacl *);
> +extern unsigned int richacl_mode_to_mask(umode_t);
> +extern unsigned int richacl_want_to_mask(unsigned int);
>  
>  #endif /* __RICHACL_H */
> diff --git a/include/uapi/linux/richacl.h b/include/uapi/linux/richacl.h
> index 08856f8..1ed48ac 100644
> --- a/include/uapi/linux/richacl.h
> +++ b/include/uapi/linux/richacl.h
> @@ -96,4 +96,48 @@
>  	RICHACE_WRITE_OWNER |					\
>  	RICHACE_SYNCHRONIZE )
>  
> +/*
> + * The POSIX permissions are supersets of the following richacl permissions:
> + *
> + *  - MAY_READ maps to READ_DATA or LIST_DIRECTORY, depending on the type
> + *    of the file system object.
> + *
> + *  - MAY_WRITE maps to WRITE_DATA or RICHACE_APPEND_DATA for files, and to
> + *    ADD_FILE, RICHACE_ADD_SUBDIRECTORY, or RICHACE_DELETE_CHILD for directories.
> + *
> + *  - MAY_EXECUTE maps to RICHACE_EXECUTE.
> + *
> + *  (Some of these richacl permissions have the same bit values.)
> + */
> +#define RICHACE_POSIX_MODE_READ (			\
> +		RICHACE_READ_DATA |			\
> +		RICHACE_LIST_DIRECTORY)
> +#define RICHACE_POSIX_MODE_WRITE (			\
> +		RICHACE_WRITE_DATA |			\
> +		RICHACE_ADD_FILE |			\
> +		RICHACE_APPEND_DATA |			\
> +		RICHACE_ADD_SUBDIRECTORY |		\
> +		RICHACE_DELETE_CHILD)
> +#define RICHACE_POSIX_MODE_EXEC RICHACE_EXECUTE
> +#define RICHACE_POSIX_MODE_ALL (			\
> +		RICHACE_POSIX_MODE_READ |		\
> +		RICHACE_POSIX_MODE_WRITE |		\
> +		RICHACE_POSIX_MODE_EXEC)
> +
> +/*
> + * These permissions are always allowed no matter what the acl says.
> + */
> +#define RICHACE_POSIX_ALWAYS_ALLOWED (			\
> +		RICHACE_SYNCHRONIZE |			\
> +		RICHACE_READ_ATTRIBUTES |		\
> +		RICHACE_READ_ACL)
> +
> +/*
> + * The owner is implicitly granted these permissions under POSIX.
> + */
> +#define RICHACE_POSIX_OWNER_ALLOWED (			\
> +		RICHACE_WRITE_ATTRIBUTES |		\
> +		RICHACE_WRITE_OWNER |			\
> +		RICHACE_WRITE_ACL)
> +
>  #endif /* __UAPI_RICHACL_H */

Other than the confusing comment, this looks ok.

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