On Thu, Aug 31, 2017 at 01:56:34PM -0700, Chenbo Feng wrote:
> From: Chenbo Feng <fengc@xxxxxxxxxx>
>
> Introduce a pointer into struct bpf_map to hold the security information
> about the map. The actual security struct varies based on the security
> models implemented. Place the LSM hooks before each of the unrestricted
> eBPF operations, the map_update_elem and map_delete_elem operations are
> checked by security_map_modify. The map_lookup_elem and map_get_next_key
> operations are checked by securtiy_map_read.
>
> Signed-off-by: Chenbo Feng <fengc@xxxxxxxxxx>
...
> @@ -410,6 +418,10 @@ static int map_lookup_elem(union bpf_attr *attr)
> if (IS_ERR(map))
> return PTR_ERR(map);
>
> + err = security_map_read(map);
> + if (err)
> + return -EACCES;
> +
> key = memdup_user(ukey, map->key_size);
> if (IS_ERR(key)) {
> err = PTR_ERR(key);
> @@ -490,6 +502,10 @@ static int map_update_elem(union bpf_attr *attr)
> if (IS_ERR(map))
> return PTR_ERR(map);
>
> + err = security_map_modify(map);
I don't feel these extra hooks are really thought through.
With such hook you'll disallow map_update for given map. That's it.
The key/values etc won't be used in such security decision.
In such case you don't need such hooks in update/lookup at all.
Only in map_creation and object_get calls where FD can be received.
In other words I suggest to follow standard unix practices:
Do permissions checks in open() and allow read/write() if FD is valid.
Same here. Do permission checks in prog_load/map_create/obj_pin/get
and that will be enough to jail bpf subsystem.
bpf cmds that need to be fast (like lookup and update) should not
have security hooks.
