Re: [PATCH v3] add group restriction bitmap

stsp
2024-10-01T13:36:53Z

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?