Re: [RFC v7 27/41] richacl: Create richacl from mode values

[J. Bruce Fields]

On Sat, Sep 05, 2015 at 12:27:22PM +0200, Andreas Gruenbacher wrote:
> A file can have "no acl" in the sense that only the file mode permission
> bits determine access.  In that case, the getxattr system call fails with
> errno == ENODATA (No such attribute).
> 
> Over the NFSv4 protocol, a file always has an acl, and we convert the file
> mode permission bits into an equivalent acl with richacl_from_mode.  Such
> "trivial" acls can be converted back to a file mode with
> richacl_equiv_mode.

Reviewed-by: J. Bruce Fields <bfields@xxxxxxxxxx>

> 
> Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
> ---
>  fs/richacl_compat.c     | 88 +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/richacl.h |  1 +
>  2 files changed, 89 insertions(+)
> 
> diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
> index 9681efe..632409f 100644
> --- a/fs/richacl_compat.c
> +++ b/fs/richacl_compat.c
> @@ -840,3 +840,91 @@ richacl_apply_masks(struct richacl **acl, kuid_t owner)
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(richacl_apply_masks);
> +
> +/**
> + * richacl_from_mode  -  create an acl which corresponds to @mode
> + *
> + * The resulting acl doesn't have the RICHACL_MASKED flag set.
> + *
> + * @mode:	file mode including the file type
> + */
> +struct richacl *
> +richacl_from_mode(mode_t mode)
> +{
> +	unsigned int owner_mask = richacl_mode_to_mask(mode >> 6);
> +	unsigned int group_mask = richacl_mode_to_mask(mode >> 3);
> +	unsigned int other_mask = richacl_mode_to_mask(mode);
> +	unsigned int denied;
> +	unsigned int entries = 0;
> +	struct richacl *acl;
> +	struct richace *ace;
> +
> +	/* RICHACE_DELETE_CHILD is meaningless for non-directories. */
> +	if (!S_ISDIR(mode)) {
> +		owner_mask &= ~RICHACE_DELETE_CHILD;
> +		group_mask &= ~RICHACE_DELETE_CHILD;
> +		other_mask &= ~RICHACE_DELETE_CHILD;
> +	}
> +
> +	denied = ~owner_mask & (group_mask | other_mask);
> +	if (denied)
> +		entries++;  /* owner@ deny entry needed */
> +	if (owner_mask & ~(group_mask & other_mask))
> +		entries++;  /* owner@ allow entry needed */
> +	denied = ~group_mask & other_mask;
> +	if (denied)
> +		entries++;  /* group@ deny entry needed */
> +	if (group_mask & ~other_mask)
> +		entries++;  /* group@ allow entry needed */
> +	if (other_mask)
> +		entries++;  /* everyone@ allow entry needed */
> +
> +	acl = richacl_alloc(entries, GFP_KERNEL);
> +	if (!acl)
> +		return NULL;
> +	acl->a_owner_mask = owner_mask;
> +	acl->a_group_mask = group_mask;
> +	acl->a_other_mask = other_mask;
> +	ace = acl->a_entries;
> +
> +	denied = ~owner_mask & (group_mask | other_mask);
> +	if (denied) {
> +		ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
> +		ace->e_flags = RICHACE_SPECIAL_WHO;
> +		ace->e_mask = denied;
> +		ace->e_id.special = RICHACE_OWNER_SPECIAL_ID;
> +		ace++;
> +	}
> +	if (owner_mask & ~(group_mask & other_mask)) {
> +		ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
> +		ace->e_flags = RICHACE_SPECIAL_WHO;
> +		ace->e_mask = owner_mask;
> +		ace->e_id.special = RICHACE_OWNER_SPECIAL_ID;
> +		ace++;
> +	}
> +	denied = ~group_mask & other_mask;
> +	if (denied) {
> +		ace->e_type = RICHACE_ACCESS_DENIED_ACE_TYPE;
> +		ace->e_flags = RICHACE_SPECIAL_WHO;
> +		ace->e_mask = denied;
> +		ace->e_id.special = RICHACE_GROUP_SPECIAL_ID;
> +		ace++;
> +	}
> +	if (group_mask & ~other_mask) {
> +		ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
> +		ace->e_flags = RICHACE_SPECIAL_WHO;
> +		ace->e_mask = group_mask;
> +		ace->e_id.special = RICHACE_GROUP_SPECIAL_ID;
> +		ace++;
> +	}
> +	if (other_mask) {
> +		ace->e_type = RICHACE_ACCESS_ALLOWED_ACE_TYPE;
> +		ace->e_flags = RICHACE_SPECIAL_WHO;
> +		ace->e_mask = other_mask;
> +		ace->e_id.special = RICHACE_EVERYONE_SPECIAL_ID;
> +		ace++;
> +	}
> +
> +	return acl;
> +}
> +EXPORT_SYMBOL_GPL(richacl_from_mode);
> diff --git a/include/linux/richacl.h b/include/linux/richacl.h
> index a945f3c..f48c04e 100644
> --- a/include/linux/richacl.h
> +++ b/include/linux/richacl.h
> @@ -334,5 +334,6 @@ extern struct richacl *richacl_create(struct inode *, struct inode *);
>  
>  /* richacl_compat.c */
>  extern int richacl_apply_masks(struct richacl **, kuid_t);
> +extern struct richacl *richacl_from_mode(mode_t);
>  
>  #endif /* __RICHACL_H */
> -- 
> 2.4.3
> 
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