Re: [PATCH v3] add group restriction bitmap

[stsp]

01.10.2024 16:02, Oleg Nesterov пишет:
> On 10/01, stsp wrote:
> > 01.10.2024 14:15, Oleg Nesterov пишет:
> > > Suppose we change groups_search()
> > >
> > > 	--- a/kernel/groups.c
> > > 	+++ b/kernel/groups.c
> > > 	@@ -104,8 +104,11 @@ int groups_search(const struct group_info *group_info, kgid_t grp)
> > > 				left = mid + 1;
> > > 			else if (gid_lt(grp, group_info->gid[mid]))
> > > 				right = mid;
> > > 	-		else
> > > 	-			return 1;
> > > 	+		else {
> > > 	+			bool r = mid < BITS_PER_LONG &&
> > > 	+				 test_bit(mid, &group_info->restrict_bitmap);
> > > 	+			return r ? -1 : 1;
> > > 	+		}
> > > 		}
> > > 		return 0;
> > > 	 }
> > >
> > > so that it returns, say, -1 if the found grp is restricted.
> > >
> > > Then everything else can be greatly simplified, afaics...
> > This will mean updating all callers
> > of groups_search(), in_group_p(),
> > in_egroup_p(), vfsxx_in_group_p()
> Why? I think with this change you do not need to touch in_group_p/etc at all.
>
> > if in_group_p() returns -1 for not found
> > and 0 for gid,
> With the the change above in_group_p() returns 0 if not found, !0 otherwise.
> It returns -1 if grp != cred->fsgid and the found grp is restricted.

in_group_p() doesn't check if the
group is restricted or not.
acl_permission_check() does, but
in your example it doesn't as well.
I think you mean to move the
restrict_bitmap check upwards to
in_group_p()?
Anyway, suppose you don't mean that.
In this case:
1. in_group_p() and in_egroup_p()
  should be changed:
-  int retval = 1;
+ int retval = -1;

But their callers should not.
There are also the callers of groups_search()
in kernel/auditsc.c and they should
be updated. But they are few.
Just to be clear, is this what you suggest?

> So acl_permission_check() can simply do
>
> 	if (mask & (mode ^ (mode >> 3))) {
> 		vfsgid_t vfsgid = i_gid_into_vfsgid(idmap, inode);
> 		int xxx = vfsgid_in_group_p(vfsgid);
>
> 		if (xxx) {
> 			if (mask & ~(mode >> 3))
> 				return -EACCES;
> 			if (xxx > 0)
> 				return 0;
> 			/* If we hit restrict_bitmap, then check Others. */
> 		}
> 	}

Well, in my impl it should check
the bitmap right here, but you removed
that. Maybe you want the check elsewhere?