[PATCH bpf-next] bpf: Fix a verifier message for alloc size helper arg

From: Brendan Jackman
Date: Tue Jan 12 2021 - 07:40:00 EST


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

Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
---
kernel/bpf/verifier.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 17270b8404f1..5534e667bdb1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4319,7 +4319,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
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;
}

base-commit: e22d7f05e445165e58feddb4e40cc9c0f94453bc
--
2.30.0.284.gd98b1dd5eaa7-goog