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    Subject[PATCH v8 26/41] richacl: Apply the file masks to a richacl
    Date
    Put all the pieces of the acl transformation puzzle together for
    computing a richacl which has the file masks "applied" so that the
    standard nfsv4 access check algorithm can be used on the richacl.

    Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
    Reviewed-by: J. Bruce Fields <bfields@redhat.com>
    ---
    fs/richacl_compat.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/richacl.h | 3 ++
    2 files changed, 104 insertions(+)

    diff --git a/fs/richacl_compat.c b/fs/richacl_compat.c
    index 7e25343..c99274f 100644
    --- a/fs/richacl_compat.c
    +++ b/fs/richacl_compat.c
    @@ -726,3 +726,104 @@ richacl_isolate_group_class(struct richacl_alloc *alloc, unsigned int deny)
    }
    return 0;
    }
    +
    +/**
    + * __richacl_apply_masks - apply the file masks to all aces
    + * @alloc: acl and number of allocated entries
    + *
    + * Apply the owner mask to owner@ aces, the other mask to
    + * everyone@ aces, and the group mask to all other aces.
    + *
    + * The previous transformations have brought the acl into a
    + * form in which applying the masks will not lead to the
    + * accidental loss of permissions anymore.
    + */
    +static int
    +__richacl_apply_masks(struct richacl_alloc *alloc, kuid_t owner)
    +{
    + struct richace *ace;
    +
    + richacl_for_each_entry(ace, alloc->acl) {
    + unsigned int mask;
    +
    + if (richace_is_inherit_only(ace) || !richace_is_allow(ace))
    + continue;
    + if (richace_is_owner(ace) ||
    + (richace_is_unix_user(ace) && uid_eq(owner, ace->e_id.uid)))
    + mask = alloc->acl->a_owner_mask;
    + else if (richace_is_everyone(ace))
    + mask = alloc->acl->a_other_mask;
    + else
    + mask = alloc->acl->a_group_mask;
    + if (richace_change_mask(alloc, &ace, ace->e_mask & mask))
    + return -1;
    + }
    + return 0;
    +}
    +
    +/**
    + * richacl_apply_masks - apply the masks to the acl
    + *
    + * Transform @acl so that the standard NFSv4 permission check algorithm (which
    + * is not aware of file masks) will compute the same access decisions as the
    + * richacl permission check algorithm (which looks at the acl and the file
    + * masks).
    + *
    + * This algorithm is split into several steps:
    + *
    + * - Move everyone@ aces to the end of the acl. This simplifies the other
    + * transformations, and allows the everyone@ allow ace at the end of the
    + * acl to eventually allow permissions to the other class only.
    + *
    + * - Propagate everyone@ permissions up the acl. This transformation makes
    + * sure that the owner and group class aces won't lose any permissions when
    + * we apply the other mask to the everyone@ allow ace at the end of the acl.
    + *
    + * - Apply the file masks to all aces.
    + *
    + * - Make sure everyone is granted the other mask permissions. This step can
    + * elevate elevate permissions for the owner and group classes, which is
    + * corrected later.
    + *
    + * - Make sure that the group class is not granted any permissions from
    + * everyone@.
    + *
    + * - Make sure the owner is granted the owner mask permissions.
    + *
    + * - Make sure the owner is not granted any permissions beyond the owner
    + * mask from group class aces or from everyone@.
    + *
    + * NOTE: Depending on the acl and file masks, this algorithm can increase the
    + * number of aces by almost a factor of three in the worst case. This may make
    + * the acl too large for some purposes.
    + */
    +int
    +richacl_apply_masks(struct richacl **acl, kuid_t owner)
    +{
    + if ((*acl)->a_flags & RICHACL_MASKED) {
    + struct richacl_alloc alloc = {
    + .acl = richacl_clone(*acl, GFP_KERNEL),
    + .count = (*acl)->a_count,
    + };
    + unsigned int added = 0;
    +
    + if (!alloc.acl)
    + return -ENOMEM;
    + if (richacl_move_everyone_aces_down(&alloc) ||
    + richacl_propagate_everyone(&alloc) ||
    + __richacl_apply_masks(&alloc, owner) ||
    + richacl_set_other_permissions(&alloc, &added) ||
    + richacl_isolate_group_class(&alloc, added) ||
    + richacl_set_owner_permissions(&alloc) ||
    + richacl_isolate_owner_class(&alloc)) {
    + richacl_put(alloc.acl);
    + return -ENOMEM;
    + }
    +
    + alloc.acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED);
    + richacl_put(*acl);
    + *acl = alloc.acl;
    + }
    + return 0;
    +}
    +EXPORT_SYMBOL_GPL(richacl_apply_masks);
    diff --git a/include/linux/richacl.h b/include/linux/richacl.h
    index 832b06c..a945f3c 100644
    --- a/include/linux/richacl.h
    +++ b/include/linux/richacl.h
    @@ -332,4 +332,7 @@ extern struct richacl *richacl_inherit(const struct richacl *, int);
    extern int richacl_permission(struct inode *, const struct richacl *, int);
    extern struct richacl *richacl_create(struct inode *, struct inode *);

    +/* richacl_compat.c */
    +extern int richacl_apply_masks(struct richacl **, kuid_t);
    +
    #endif /* __RICHACL_H */
    --
    2.4.3


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