bpf: Fix ringbuf helper function compatibility

Commit 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support
for it") extended check_map_func_compatibility() by enforcing map -> helper
function match, but not helper -> map type match.

Due to this all of the bpf_ringbuf_*() helper functions could be used with
a wrong map type such as array or hash map, leading to invalid access due
to type confusion.

Also, both BPF_FUNC_ringbuf_{submit,discard} have ARG_PTR_TO_ALLOC_MEM as
argument and not a BPF map. Therefore, their check_map_func_compatibility()
presence is incorrect since it's only for map type checking.

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: Ryota Shiga (Flatt Security)
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 381d3d6f24bcb18efbf60a96bd74e05fc774ae66..49f07e2bf23b9be28c9ead67bbed185b18785632 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5150,8 +5150,6 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
        case BPF_MAP_TYPE_RINGBUF:
                if (func_id != BPF_FUNC_ringbuf_output &&
                    func_id != BPF_FUNC_ringbuf_reserve &&
-                   func_id != BPF_FUNC_ringbuf_submit &&
-                   func_id != BPF_FUNC_ringbuf_discard &&
                    func_id != BPF_FUNC_ringbuf_query)
                        goto error;
                break;
@@ -5260,6 +5258,12 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
                if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
                        goto error;
                break;
+       case BPF_FUNC_ringbuf_output:
+       case BPF_FUNC_ringbuf_reserve:
+       case BPF_FUNC_ringbuf_query:
+               if (map->map_type != BPF_MAP_TYPE_RINGBUF)
+                       goto error;
+               break;
        case BPF_FUNC_get_stackid:
                if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
                        goto error;