bpf: Fix a verifier message for alloc size helper arg

The error message here is misleading, the argument will be rejected unless
it is a known constant.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210112123913.2016804-1-jackmanb@google.com

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 17270b8..5534e66 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4319,7 +4319,7 @@ skip_type_check:
                        err = mark_chain_precision(env, regno);
        } else if (arg_type_is_alloc_size(arg_type)) {
                if (!tnum_is_const(reg->var_off)) {
-                       verbose(env, "R%d unbounded size, use 'var &= const' or 'if (var < const)'\n",
+                       verbose(env, "R%d is not a known constant'\n",
                                regno);
                        return -EACCES;
                }