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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