| Message ID | 1443391772-10171-10-git-send-email-agruenba@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Sep 28, 2015 at 12:09:00AM +0200, Andreas Gruenbacher wrote: > Doing a chmod() sets the file mode, which includes the file permission > bits. When a file has a richacl, the permissions that the richacl > grants need to be limited to what the new file permission bits allow. > > This is done by setting the file masks in the richacl to what the file > permission bits map to. The richacl access check algorithm takes the > file masks into account, which ensures that the richacl cannot grant too > many permissions. > > It is possible to explicitly add permissions to the file masks which go > beyond what the file permission bits can grant (like the > RICHACE_WRITE_ACL permission). The POSIX.1 standard calls this an > alternate file access control mechanism. A subsequent chmod() would > ensure that those permissions are disabled again. > > Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> > Reviewed-by: J. Bruce Fields <bfields@redhat.com> > --- > fs/richacl_base.c | 40 ++++++++++++++++++++++++++++++++++++++++ > include/linux/richacl.h | 1 + > 2 files changed, 41 insertions(+) > > diff --git a/fs/richacl_base.c b/fs/richacl_base.c > index fc544f7..6c69234 100644 > --- a/fs/richacl_base.c > +++ b/fs/richacl_base.c > @@ -339,3 +339,43 @@ restart: > acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED); > } > EXPORT_SYMBOL_GPL(richacl_compute_max_masks); > + > +/** > + * richacl_chmod - update the file masks to reflect the new mode > + * @mode: new file permission bits including the file type > + * > + * Return a copy of @acl where the file masks have been replaced by the file > + * masks corresponding to the file permission bits in @mode, or returns @acl > + * itself if the file masks are already up to date. Takes over a reference > + * to @acl. > + */ > +struct richacl * > +richacl_chmod(struct richacl *acl, mode_t mode) > +{ > + unsigned int x = S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD; > + unsigned int owner_mask, group_mask, other_mask; > + struct richacl *clone; > + > + owner_mask = richacl_mode_to_mask(mode >> 6) & ~x; > + group_mask = richacl_mode_to_mask(mode >> 3) & ~x; > + other_mask = richacl_mode_to_mask(mode) & ~x; > + > + if (acl->a_owner_mask == owner_mask && > + acl->a_group_mask == group_mask && > + acl->a_other_mask == other_mask && > + (acl->a_flags & (RICHACL_WRITE_THROUGH | RICHACL_MASKED))) I think you meant to require both of those bits to be set. --b. > + return acl; > + > + clone = richacl_clone(acl, GFP_KERNEL); > + richacl_put(acl); > + if (!clone) > + return ERR_PTR(-ENOMEM); > + > + clone->a_flags |= (RICHACL_WRITE_THROUGH | RICHACL_MASKED); > + clone->a_owner_mask = owner_mask; > + clone->a_group_mask = group_mask; > + clone->a_other_mask = other_mask; > + > + return clone; > +} > +EXPORT_SYMBOL_GPL(richacl_chmod); > diff --git a/include/linux/richacl.h b/include/linux/richacl.h > index e81144a..e00f313 100644 > --- a/include/linux/richacl.h > +++ b/include/linux/richacl.h > @@ -298,5 +298,6 @@ extern int richacl_masks_to_mode(const struct richacl *); > extern unsigned int richacl_mode_to_mask(mode_t); > extern unsigned int richacl_want_to_mask(unsigned int); > extern void richacl_compute_max_masks(struct richacl *); > +extern struct richacl *richacl_chmod(struct richacl *, mode_t); > > #endif /* __RICHACL_H */ > -- > 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
2015-09-28 17:28 GMT+02:00 J. Bruce Fields <bfields@fieldses.org>: > On Mon, Sep 28, 2015 at 12:09:00AM +0200, Andreas Gruenbacher wrote: >> + (acl->a_flags & (RICHACL_WRITE_THROUGH | RICHACL_MASKED))) > > I think you meant to require both of those bits to be set. Yes, indeed. Thanks, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/richacl_base.c b/fs/richacl_base.c index fc544f7..6c69234 100644 --- a/fs/richacl_base.c +++ b/fs/richacl_base.c @@ -339,3 +339,43 @@ restart: acl->a_flags &= ~(RICHACL_WRITE_THROUGH | RICHACL_MASKED); } EXPORT_SYMBOL_GPL(richacl_compute_max_masks); + +/** + * richacl_chmod - update the file masks to reflect the new mode + * @mode: new file permission bits including the file type + * + * Return a copy of @acl where the file masks have been replaced by the file + * masks corresponding to the file permission bits in @mode, or returns @acl + * itself if the file masks are already up to date. Takes over a reference + * to @acl. + */ +struct richacl * +richacl_chmod(struct richacl *acl, mode_t mode) +{ + unsigned int x = S_ISDIR(mode) ? 0 : RICHACE_DELETE_CHILD; + unsigned int owner_mask, group_mask, other_mask; + struct richacl *clone; + + owner_mask = richacl_mode_to_mask(mode >> 6) & ~x; + group_mask = richacl_mode_to_mask(mode >> 3) & ~x; + other_mask = richacl_mode_to_mask(mode) & ~x; + + if (acl->a_owner_mask == owner_mask && + acl->a_group_mask == group_mask && + acl->a_other_mask == other_mask && + (acl->a_flags & (RICHACL_WRITE_THROUGH | RICHACL_MASKED))) + return acl; + + clone = richacl_clone(acl, GFP_KERNEL); + richacl_put(acl); + if (!clone) + return ERR_PTR(-ENOMEM); + + clone->a_flags |= (RICHACL_WRITE_THROUGH | RICHACL_MASKED); + clone->a_owner_mask = owner_mask; + clone->a_group_mask = group_mask; + clone->a_other_mask = other_mask; + + return clone; +} +EXPORT_SYMBOL_GPL(richacl_chmod); diff --git a/include/linux/richacl.h b/include/linux/richacl.h index e81144a..e00f313 100644 --- a/include/linux/richacl.h +++ b/include/linux/richacl.h @@ -298,5 +298,6 @@ extern int richacl_masks_to_mode(const struct richacl *); extern unsigned int richacl_mode_to_mask(mode_t); extern unsigned int richacl_want_to_mask(unsigned int); extern void richacl_compute_max_masks(struct richacl *); +extern struct richacl *richacl_chmod(struct richacl *, mode_t); #endif /* __RICHACL_H */